Patients with coronavirus disease 2019 (COVID-19), including those with mild or no symptoms, may readily transmit the disease given the high person-to-person infectivity in the latent period of COVID-19; this transmission could threaten public health.1 Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative virus of COVID-19, replicates efficiently in the upper respiratory tract and appears to cause delayed onset of symptoms; therefore, COVID-19 poses considerable challenges to the health system.2 3 Thus, there is a need to rapidly identify infected individuals who exhibit only mild symptoms. In March to April 2020, the Hospital Authority, Hong Kong, established a temporary test centre (TTC) at the AsiaWorld-Expo (AWE), which is within the Hong Kong International Airport complex on Lantau Island. The AWE TTC offered tests for individuals with mild symptoms among those arriving at the airport, as well as those engaged in home quarantine in Hong Kong, for the early detection of SARS-CoV-2 infection that could be managed by early isolation and intervention.4 Asymptomatic individuals were tested at a different facility within AWE operated by the Department of Health. This study reviewed the characteristics and outcomes of individuals who attended the AWE TTC for COVID-19 testing.

This retrospective cross-sectional study evaluated the characteristics and outcomes of individuals who attended the AWE TTC during its operation from 20 March 2020 to 19 April 2020. All individuals who attended the AWE TTC were included, with the exception of patients who were transferred out of the AWE TTC to accident and emergency departments before they could undergo COVID-19 testing. Infection control measures implemented at the AWE TTC were reported previously.5 Ethics approval was obtained from the Kowloon West Cluster Research Ethics Committee, Hospital Authority.

Clinical characteristics assessed in this study were fever, chills, cough, runny nose, sore throat, vomiting, diarrhoea, fatigue, myalgia, headache, anosmia, history of hypertension, history of diabetes mellitus, history of chronic respiratory disease, and history of malignancy. Epidemiological parameters assessed in this study were age, sex, district of residence, travel history, occupational exposure, contact history, and clustering history. These data were collected using a standard clinical assessment template by duty medical officers in the Clinical Management System of the Hospital Authority. The primary outcome was positive or negative SARS-CoV-2 test results, according to reverse transcription polymerase chain reaction analyses of pooled nasopharyngeal and throat swabs collected at the AWE TTC.

The positivity rate with 95% confidence interval (CI) was calculated. Demographic and clinical characteristics of individuals with positive and negative test results were compared using Pearson’s Chi squared test, Fisher’s exact test, or the Mann-Whitney U test, as appropriate. Adjusted odds ratios with 95% Wald CIs were derived using multivariable binary logistic regression to assess the associations of clinical characteristics with SARS-CoV-2 positive test results. Partially standardised beta coefficients were used to compare the strengths of associations between individual clinical characteristics and SARS-CoV-2 test results; a greater absolute value of the partially standardised beta coefficient was indicative of a stronger association. Ridge regression was performed to implement penalisation for management of the sparse data bias elicited by the low prevalences of some clinical characteristics.6 7 The tuning parameter λ was identified as the optimal value that resulted in minimal error via 10-fold cross-validation; as the tuning parameter λ became larger, the estimated odds ratio decreased towards a value of 1. Bootstrapping was used to construct 95% CIs with 100 bootstrap replications. Statistical analyses were performed using R version 3.6.1 with “glmnet” and “boot” packages. A P value of <0.05 was considered statistically significant.

In total, 1286 individuals attended the AWE TTC for COVID-19 testing (Table 1). Of these 1286 attendees, 1258 were included in the analysis after the exclusion of three attendees with important missing data and 25 attendees who were immediately referred to regional accident and emergency departments because of severe symptoms requiring investigation or therapy beyond the capacity of the AWE TTC. These severe symptoms included shortness of breath (n=8); high fever (n=5); chest discomfort (n=5); acute gastrointestinal symptoms (n=4); and acute ear, nose, throat symptoms (n=3). Finally, 1242 individuals were involved in the analysis because 16 individuals attended the AWE TTC twice due to ongoing or changing symptoms; the remaining 1226 individuals attended the AWE TTC only once for testing. Among the 1258 included tests, five showed indeterminate results during the first sampling, while subsequent re-tests revealed negative results; thus, there were 86 positive SARS-CoV-2 results with a positivity rate of 6.84% (95% CI=5.57%-8.37%). During the study period, the maximum number of attendees (n=79) was recorded on 30 March 2020 and the highest daily number of positive test results (n=8) was recorded on 6 April 2020. Attendees with positive test results were all admitted to public hospitals through central coordination for further clinical assessment and treatment.

Most attendees were aged 15 to 24 years (740/1258, 58.8%). Furthermore, most attendees (n=1190, 94.6%) were incoming travellers from the United Kingdom, the United States, Canada, Australia, and other parts of the world (Table 2). A history of travel to the United Kingdom was significantly associated with positive test results (69.8% of positive test results vs 51.9% of negative test results; P=0.001). Cluster or contact history was reported by 32.6% of attendees with positive test results and 10.7% of attendees with negative test results (P<0.001). The most frequently reported symptoms among all attendees were cough (60.8%), sore throat (46.9%), and runny nose (34.6%). Symptoms were reported by 86.0% and 96.3% of individuals with positive and negative test results, respectively.

The clinical characteristics most strongly associated with a positive test result were anosmia (ridge regression adjusted odds ratio [OR_adj]=8.30; 95% CI=1.12-127.09) and fever (OR_adj=1.32; 95% CI=1.02-3.28) [Table 3]. Sore throat was significantly associated with a negative test result (OR_adj= 0.86; 95% CI=0.36-0.99). Other characteristics (ie, cough, runny nose, fatigue, headache, myalgia, vomiting, chills, and diarrhoea) did not show significant associations with positive or negative test results, according to ridge regression analysis.

To the best of our knowledge, this is the first study in Hong Kong to explore the clinical characteristics of attendees at a public TTC established by the Hospital Authority in response to a worldwide pandemic. Early identification and early containment have been critical strategies adopted by the Centre for Health Protection, Hong Kong to address the pandemic. Locally, the first imported case in an individual with a history of travel outside mainland China was reported on 4 March 2020. This was followed by a large number of imported cases involving returning travellers, including 245 students from the United Kingdom and the United States who had positive test results; the maximum number of cases (n=65) was reported on 27 March 2020.8 The establishment of a TTC was a crucial public health intervention to address the influx of returning overseas travellers during the worldwide spread of COVID-19 beginning in March 2020. Given the potential transmission of COVID-19 among individuals with relatively mild clinical symptoms, early identification of SARS-CoV-2 infection by reverse transcription polymerase chain reaction testing is crucial for reducing disease spread.9 The AWE TTC was equipped with extensive testing capacity for the target population of individuals with mild disease symptoms.

Among AWE TTC attendees, the majority of positive test results were recorded in young individuals (aged 15-24 years; 40 of 86 cases), who comprised 46.5% of total attendees with positive test results. Notably, this proportion was greater than the proportion reported by the Centre for Health Protection concerning individuals in the same age-group (289 of 1084 cases; 26.7%) among all COVID-19 cases in Hong Kong during the study period. This is potentially attributable to the targeted testing strategy that focused on incoming overseas students, which was implemented after the Hong Kong Government announced compulsory testing and quarantine for all arriving travellers beginning on 19 March 2020.10 We previously reported that most individuals could be tested on-site; moreover, the AWE TTC fulfilled its gatekeeping role by reducing the number of hospital admissions by 36 patients per day during its 31 days of operation.5

Primary care providers and emergency physicians have performed important gatekeeping roles in the early identification of individuals with COVID-19. However, a local Family Physician survey revealed that this gatekeeping task is challenging because of the non-specific and mild disease manifestations in many individuals with SARS-CoV-2 infections.11 In Hong Kong, among 1084 confirmed cases reported between January 2020 and May 2020, symptoms were reported by 859 (79.2%) affected patients. The five most common symptoms reported by Hong Kong patients with COVID-19 included cough (436, 50.8%), fever (428, 49.8%), sore throat (174, 20.3%), headache (98, 11.4%), and runny nose (97, 11.3%). The remaining 225 patients (20.8%) were asymptomatic.8 An early study of 41 patients in Wuhan, published in January 2020, revealed that the most common symptoms at onset of illness were fever (98%), cough (76%), and myalgia or fatigue (44%).12 A multicentre study in Shanghai reported that the most common symptoms among 1004 patients with positive test results were fever (84%), cough (62%), and fatigue (25%).13 Our study reviewed the clinical characteristics and outcomes of relatively healthy individuals in Hong Kong whose demographic characteristics were similar to those of the general practice population; we found that the three most common symptoms among infected individuals were cough, fever, and sore throat (Table 1), consistent with the findings in a local study by the Centre for Health Protection.6 In addition to the usual upper respiratory tract symptoms, our results showed that fever and anosmia were strongly associated with positive test results. These findings provide important guidance for gatekeeping physicians to carefully consider symptoms such as anosmia (a relatively uncommon symptom in primary care consultations), which was present in 22.1% of our attendees with positive test results and only 0.3% of attendees with negative test results. Evidence of such symptoms should alert clinicians to the potential presence of COVID-19. A study performed in South Korea revealed that acute olfactory disturbance was present in 15.3% of patients (488/3191) in the early stage of COVID-19. Its prevalence was significantly more common among female patients and younger individuals (P=0.01 and P<0.001, respectively).14 A study performed in the Netherlands showed that anosmia was present in 47% of individuals with positive test results and was strongly associated with SARS-CoV-2 positivity (odds ratio=23.0; 95% CI=8.2%-64.8%).15 In our study, the OR_adj for anosmia was 8.30 (95% CI=1.12-127.09), indicating a strong association between anosmia and a positive test result. However, this result should be interpreted cautiously, considering the potential for over- or under-reporting of the symptom at a cross-sectional encounter, the co-existence of other conditions that may lead to olfactory disturbance, and the timing of illness presentation. The probability of identifying an infected individual depends on the incubation period and the proportion of individuals with subclinical disease.16 Symptoms alone might not be reliable for diagnosis. Early testing is critical for the early identification of both symptomatic and asymptomatic individuals. This approach has been particularly essential with worsening disease spread, which has required stricter infection control measures since July 2020.17 18

Of the 1286 AWE TTC attendees, 25 (1.94%) with severe symptoms were immediately transferred to the accident and emergency departments; these attendees did not undergo testing at the AWE TTC. The inclusion and exclusion criteria used in this TTC could be useful for planning and implementation efforts (in terms of referral criteria) if similar centres must be established in future emergency circumstances. Notably, this type of centre is considered safe and efficient for screening to reduce community disease spread19 and could be more readily implemented to manage an infectious disease, compared with vaccination and effective antiviral therapy.20

The strengths of this study were its large sample size and centralised setting that allowed coverage of the entire Hong Kong population (regardless of residential location) with elevated COVID-19 risk, including those arriving at the airport and those under home quarantine; all AWE TTC attendees exhibited mild disease symptoms similar to those of potentially infected individuals encountered in primary care settings. The limitations of this study included its retrospective data collection based on electronic health records. Investigators could not verify the reported conditions of the AWE TTC attendees or recover any important missing data. Nevertheless, all AWE TTC attendees were assessed by physicians with a standard questionnaire for documentation of demographics and symptoms; they were also tested by reverse transcription polymerase chain reaction analyses of standard pooled nasopharyngeal and throat swabs, which provided clear positive and negative results that facilitated data analysis. Another limitation of the study involved its cross-sectional study design. The epidemiological information and clinical symptoms collected during patient assessment at the AWE TTC might not be identical to those of post-admission situations because the patients’ conditions might have changed in a manner dependent on the timing of presentation. For example, a study of 1099 patients in China found that fever was present in 43.8% of patients on admission, but was present in 88.7% of patients during hospitalisation.21 Importantly, the present study could not offer predictive value or relative risk projection on the basis of its epidemiological and clinical findings. Further studies with a longitudinal design may provide useful epidemiological and clinical insights.

In some individuals, COVID-19 causes mild initial symptoms despite its high infectivity; thus, there is a need for early identification of individuals with SARS-CoV-2 infection who exhibit mild symptoms. The establishment of a TTC was successful in identifying infected individuals in a large-scale, high-turnover setting, thereby reducing the testing burden in secondary and tertiary healthcare facilities. Gatekeeping healthcare providers should carefully consider the epidemiological and clinical manifestations of COVID-19 and be vigilant in arranging appropriate early testing to reduce community spread.

Concept or design: WLH Leung, ELM Yu.
Acquisition of data: WLH Leung.
Analysis or interpretation of data: WLH Leung, ELM Yu.
Drafting of the manuscript: WLH Leung.
Critical revision of the manuscript for important intellectual content: All authors.

All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

All authors have disclosed no conflicts of interest.

The authors acknowledge all workers involved in the setup and operation of the temporary test centre at AsiaWorld-Expo, Hong Kong.

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

This study was approved by the Kowloon West Cluster Research Ethics Committee, Hospital Authority [Ref KW/EX-20-085(148-09)]. The Ethics Committee waived the need for patient consent for this retrospective study.

1. Bai Y, Yao L, Wei T, et al. Presumed asymptomatic carrier transmission of COVID-19. JAMA 2020;323:1406-7. Crossref

2. Heymann DL, Shindo N, WHO Scientific and Technical Advisory Group for Infectious Hazards. COVID-19: what is next for public health? Lancet 2020;395:542-5. Crossref

3. Chan JF, Yuan S, Kok KH, et al. A familial cluster of pneumonia associated with the 2019 novel coronavirus indicating person-to-person transmission: a study of a family cluster. Lancet 2020;395:514-23. Crossref

4. Hong Kong SAR Government. Temporary test centres speed up tests for people upon arrival. Available from: https://www.info.gov.hk/gia/general/202003/19/P2020031900664.htm. Accessed 11 Jul 2020.

5. Wong SC, Leung M, Lee LL, Chung KL, Cheng VC. Infection control challenge in setting up a temporary test centre at Hong Kong International Airport for rapid diagnosis of COVID-19 due to SARS-CoV-2. J Hosp Infect 2020;105:571-3. Crossref

6. Greenland S, Mansournia MA, Altman DG. Sparse data bias: a problem hiding in plain sight. BMJ 2016;352:i1981. Crossref

7. Doerken S, Avalos M, Lagarde E, Schumacher M. Penalized logistic regression with low prevalence exposures beyond high dimensional settings. PloS One 2019;14:e0217057. Crossref

8. Lam HY, Lam TS, Wong CH, et al. The epidemiology of COVID-19 cases and the successful containment strategy in Hong Kong–January to May 2020. Int J Infect Dis 2020;98:51-8. Crossref

9. To KK, Yuen KY. Responding to COVID-19 in Hong Kong. Hong Kong Med J 2020;26:164-6. Crossref

10. Hong Kong SAR Government. Compulsory quarantine law gazetted. Available from: https://www.news.gov.hk/eng/20 20/03/20200318/20200318_211807_723.html. Accessed 11 Jul 2020.

11. Yu EY, Leung WL, Wong SY, Liu KS, Wan EY, HKCFP Executive and Research Committee. How are family doctors serving the Hong Kong community during the COVID-19 outbreak? A survey of HKCFP members. Hong Kong Med J 2020;26:176-83. Crossref

12. Huang C, Wang Y, Li X, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet 2020;395:497-506. Crossref

13. Mao B, Liu Y, Chai YH, et al. Assessing risk factors for SARS-CoV-2 infection in patients presenting with symptoms in Shanghai, China: a multicentre, observational cohort study. Lancet Digit Health 2020;2:e323-30. Crossref

14. Lee Y, Min P, Lee S, Kim SW. Prevalence and duration of acute loss of smell or taste in COVID-19 patients. J Korean Med Sci 2020;35:e174. Crossref

15. Tostmann A, Bradley J, Bousema T, et al. Strong associations and moderate predictive value of early symptoms for SARS-CoV-2 test positivity among healthcare workers, the Netherlands, March 2020. Euro Surveill 2020;25:2000508. Crossref

16. Gostic K, Gomez AC, Mummah RO, Kucharski AJ, Lloyd-Smith JO. Estimated effectiveness of symptom and risk screening to prevent the spread of COVID-19. Elife 2020;9:e55570. Crossref

17. Hong Kong SAR Government. Social distancing rules to be tightened. Available from: https://www.news.gov.hk/eng/2020/07/20200709/20200709_175812_722.html. Accessed 11 Jul 2020.

18. Hong Kong SAR Government. Government further tightens social distancing measures. Available from: https://www.info.gov.hk/gia/general/202007/27/P2020072700650.htm. Accessed 27 Jul 2020.

19. Kwon KT, Ko JH, Shin H, Sung M, Kim JY. Drive-through screening center for COVID-19: a safe and efficient screening system against massive community outbreak. J Korean Med Sci 2020;35:e123. Crossref

20. Peto J. Covid-19 mass testing facilities could end the epidemic rapidly. BMJ 2020;368:m1163. Crossref

21. Guan WJ, Ni ZY, Hu Y, et al. Clinical characteristics of coronavirus disease 2019 in China. N Engl J Med 2020;382:1708-20. Crossref

Atopic dermatitis (AD) or eczema, asthma, and allergic rhinitis (AR) are associated diseases involved in the atopic march.1 2 3 Many children with AD develop asthma and/or AR when they reach adulthood. There are a number of clinical and laboratory tools to evaluate atopic status in patients with AD. The bronchial challenge test (BCT) is an important tool that evaluates airway hyperresponsiveness in patients with asthma. Responsive patients develop acute contraction of smooth muscles lining the bronchi, resulting in sudden narrowing and obstruction of the airway. The extent of airway narrowing can increase during periods of exacerbation and decrease during treatment with anti-inflammatory drugs.4 The inhalation of histamine or methacholine produces direct airway responses. Histamine maximises bronchial obstruction by directly activating H1 histamine receptors during inhalation challenge. It also stimulates nasal and mucus secretion, promotes vasodilation, and increases vascular permeability. Methacholine is a synthetic derivative of the acetylcholine neurotransmitter, which directly stimulates M3 muscarinic receptors on airway smooth muscles to induce bronchoconstriction.4 A low inhaled dose could trigger a high degree of airway hyperresponsiveness in patients with asthma.

In BCT, methacholine and histamine stimulate an increase in cyclic guanosine monophosphate level and a decrease in cyclic adenosine monophosphate level, thus contributing to smooth muscle contraction.5 Immediate bronchoconstriction reactions can begin immediately after challenge; the peak is within approximately 30 minutes. The effect is typically reversible within 1.5 to 2 hours with the aid of bronchodilators. This is regarded as a type 1 hypersensitivity reaction mediated by immunoglobulin E (IgE), which is present in patients with hypersensitivity pneumonitis, asthma, and other atopic diseases. Immunoglobulin E has a specific role in the induction of many allergic reactions as evidenced by its high serum level in patients with allergic diseases and those with atopic diseases.6 7

Distinct dosages are used for the inhalation of methacholine and histamine, but the inhalation challenge procedures are identical.8 During the test, a diluent is provided via nebulisation for five inhalations, followed by nebulisation of the test compound at low concentrations. A spirometry test is conducted after each dilution to assess the patient’s pulmonary function. A reduction in forced expiratory volume in 1 second (FEV₁) of ≥20% signifies a positive response and the end of the test. A bronchodilator is then provided to counteract the effects of the test compound. In subsequent tests, the dose that provokes the desirable ≥20% reduction of FEV₁ is employed.5

There are several contra-indications for the BCT. Patients with reduced lung function as evidenced by a low FEV₁ level in baseline spirometry may be predisposed to a greater risk of serious adverse events.9 A prior bronchodilator FEV₁ <60% predicted or FEV₁ <75% predicted during a single high stimulus (eg, exercise) are relative contra-indications.10 Airway obstruction in baseline spirometry supplemented with clinical features of asthma is sufficient for diagnosis and the BCT is unnecessary. Furthermore, an inability to follow the instructions of the spirometry test undermines the BCT quality.11 Individuals with a history of cardiovascular problems, increased intracranial pressure, or recent eye surgery may experience enhanced cardiovascular stress as a consequence of bronchoconstriction during the BCT and should not be subjected to this test.4 10 In general, patients with asthma respond to methacholine and histamine even at low concentrations, such that 84% and 73% react to the above compounds, respectively.12

This study aimed to investigate whether personal characteristics, history of allergen exposure, skin prick test results, clinical assessment scores, laboratory parameters, and personal or family histories of atopic diseases are associated with a positive BCT result in paediatric patients with AD. The result is useful in counselling parents and patients with AD and risks of asthma in the family.

This retrospective case series included patients with AD who were treated at the paediatric dermatology clinic of a university hospital from January 2000 to November 2017; patients who had undergone the BCT were retrospectively selected for analysis. All selected patients were Chinese and aged >8 years (the minimum age at which patients can complete the BCT in our hospital pulmonology laboratory).4 11 13 Data concerning the following clinical and personal characteristics were obtained from the patients’ medical records: AD onset age, history of other atopy (ie, AR and atopic asthma), history of atopy (ie, AD, atopic asthma and AR) in parents and siblings, potential allergen exposure (ie, pet ownership and tobacco smoking), and AD treatment history (ie, allergen avoidance and use of traditional Chinese medicine). Clinical laboratory parameters obtained from the electronic patient record system included BCT results, highest serum IgE level, highest eosinophil counts (absolute and relative), and skin prick test results for allergic response to dust mite, cockroach, dogs, cats, and food allergens.

Atopic dermatitis severity was clinically scored by the SCORing Atopic Dermatitis (SCORAD), skin hydration, and transepidermal water loss (TEWL) during follow-up visits.14 The SCORAD is a mathematically derived score that considers the extent, severity, and subjective symptoms of AD.15 The skin hydration and TEWL were measured using Courage and Khazaka equipment, which indirectly measures the density gradient of water evaporation from the skin by two pairs of sensors that determine the temperature and relative humidity, respectively.16

The IBM SPSS Statistics (Windows version 20) was used to conduct all statistical analysis. Student’s t test was conducted to compare continuous variables between groups; these data were expressed as mean ± standard deviation. The Chi squared test (or Fisher’s exact test) was conducted to compare categorical variables between groups; these data were expressed as number (%). A P value of <0.05 was considered statistically significant. Backward binary logistic regression analysis was then used to analyse the data. The variable with the highest P value was removed at each step until the final equation included only variables with P<0.05.

The New Territories East Cluster and The Chinese University of Hong Kong ethics committee approved this retrospective study.

In total, 579 patients with AD were included in this study; 284 had confirmed BCT results. Patient follow-up data were censored as of November 2017 to February 2018. Of the 284 patients with BCT results, 106 had a positive result (BCT-positive group), while 178 had a negative result (BCT-negative group). There were significant differences in current age (P=0.039) and the age at BCT performance (P=0.004) between groups (Table 1).

A positive BCT result was associated with personal history of asthma (P<0.0005) and a sibling with asthma, compared with patients with a negative BCT result (28.6% vs 6.8%; P=0.048) [Table 1].

There were no significant associations between BCT results and personal AR, maternal atopy (specifically, asthma, AR, AD), paternal atopy (specifically asthma, AR, AD), siblings’ AR, and siblings’ AD. Moreover, BCT results were not associated with a history of skin prick response to allergens, including dust mites (Table 1).

There were no significant associations between BCT results and clinical measures of AD severity, in terms of objective SCORAD score, SH, or TEWL. Results of BCT were associated with markers of allergic reactions, including (highest) serum IgE (P=0.045), highest eosinophil count (P=0.017), and sensitisation to food allergens in skin prick test (P=0.027). However, they were not associated with other allergens tested in the skin prick panel, such as aeroallergens from dust mites, cockroaches, dogs, or cats (Table 1). Results of BCT had no significant association with previous exposure to potential environmental irritants, including smoking in the household, incense burning, cat ownership, or dog ownership. There were no significant associations between BCT results and history of AD treatment, including food avoidance and traditional Chinese medicine usage (Table 1).

Of the 284 patients with AD and confirmed BCT results, 142 patients had all relevant data available. Backward binary logistic regression (n=142) showed significant associations between a positive BCT result and a personal history of asthma (adjusted odds ratio [aOR]=4.05; 95% confidence interval [CI]=1.92-8.55; P<0.0005) and sibling atopy (aOR=2.25; 95% CI=1.03-4.92; P=0.042). However, it did not show associations with AD severity, young age at AD onset, personal history of AR, aeroallergen (including dust mite, cockroach, cat and dog hair) and food allergen sensitisation, parental history of atopy, or highest serum IgE level and blood eosinophil count (Table 2).

In our study, backward binary logistic regression analysis showed that a positive BCT result was independently and positively associated with a personal history of asthma in patients with AD. The Global Initiative for Asthma, a medical guidelines organisation, has established a standard for the diagnosis of asthma, which recommends the documentation of variable expiratory airflow limitation. Although asthma is principally a clinical diagnosis, the BCT can aid in this assessment.17 The sensitivity of the BCT in complementing asthma diagnosis is generally believed to approach 100% if a cut point is set at 8 mg/mL or 16 mg/mL, using a non-deep inhalation method.18 Cockcroft18 showed that when the PC20 (ie, histamine provocative concentration causing a 20% drop in FEV₁) cut-off was set at ≤8 mg/mL, all individuals with current symptomatic asthma could be identified in a random population with a sensitivity of nearly 100%.1

However, a recent study indicated that the prevalence of a positive BCT result in children with asthma is approximately 70%.19 This is attributed to the potential effects of several factors associated with a positive BCT result, especially using the methacholine challenge test; these factors include AR, respiratory infections, and chronic respiratory conditions (eg, bronchitis and chronic obstructive pulmonary disease).19 Despite its limitations, including that the test can only be used in older children, the BCT remains a useful tool for the diagnosis of asthma (Table 2). Clinical usage of the BCT in the diagnosis of asthma is based on its high sensitivity and negative predictive value, but a positive BCT result itself is not confirmatory for asthma.17 20

In this study of 284 patients with BCT results, the aOR of a positive BCT result for asthma in patients with AD was 4.05, implying that patients with AD who have a positive BCT result are fourfold more likely to have asthma. This is consistent with the findings of a 2015 meta-analysis that included 31 studies conducted in 102 countries; the risk ratio of AD to other two atopic disorders, including AR and asthma, was 4.24 (95% CI=3.75-4.79). The results demonstrated a clear relationship between the skin and the airways.21 Riiser et al22 followed 530 children who completed the BCT at the age of 10 years and underwent structured reviews and clinical examinations at the age of 16 years; they examined the predictability of BCT results for active asthma in adolescence. The investigators concluded that the presence of bronchial hyperreactivity (BHR), especially severe BHR, was a significant risk factor and that provocative dose 20 resulting in 20% decrease in FEV₁ in a positive test alone explained 10% of the variation in active asthma.22 Another study showed similar findings, in that airway hyperresponsiveness independently predicted asthma symptoms in childhood (aOR=2.6; 95% CI=1.8-3.7).23 Our results concurred with those of the above studies, indicating that BHR could develop before active asthma symptoms appear and that BCT might indeed predict asthma incidence in children with AD.

Atopy is known to have a strong hereditary component. A family study of 188 Caucasian patients and their family members demonstrated a twofold increase in risk of developing AD and atopy with each additional first-degree relative who exhibited atopy.24 Furthermore, a maternal history of atopic disease was associated with an elevated IgE level among infants. For maternal asthma, this association was only evident in infant girls.25 Hong Kong has a relatively high prevalence of single-child families; however, among patients with siblings, positive relationships with sibling atopy have been found.1 2 In our study, among 106 patients with a positive BCT result, rates of maternal, paternal, and sibling atopy were 40.0%, 53.7%, and 64.1%, respectively. A positive BCT result was independently and positively associated with sibling atopy (aOR=2.25; 95% CI=1.03-4.92; P=0.042), which includes asthma, AR, and/or AD. However, no associations with parental atopy were found. Patients with positive BCT results are presumably more likely to have siblings with atopy, in that 64.1% of patients with positive BCT results had siblings with atopy, compared with 52.7% of patients with negative BCT results. The most likely explanations of the association with siblings involve genetic heredity and similar epigenetic factors in childhood. Siblings of patients with atopy are predisposed to an inherited tendency to developing IgE antibodies to specific allergens, with subsequent hypersensitivity reactions. Several twin studies were conducted to demonstrate the roles of genetic and environmental factors on atopy. A multivariate genetic analysis with a total of 575 twin participants revealed that atopic conditions were associated with genetic and environmental factors; it also showed that different phenotypic conditions shared common genetic backgrounds.26 Family and twin studies have shown that genetic inheritance plays an important role in the development of atopy; they identified 79 genes associated with asthma or atopy in more than one population.27 Despite genetic involvement, atopic conditions are highly heterogeneous and involve complex epigenetic factors. The atopic state is presumably related to a pre-existing genotype that is activated by environmental factors.28 Both the factors themselves and duration of exposure are important. Several epigenetic factors with an impact on atopy have been established; these can be further subcategorised into prenatal, infancy, childhood, and adulthood types.29 Affected children and their siblings are exposed to common environmental factors in their childhood, such as tobacco smoke, allergic sensitisation, infections, and diet.

There was minimal information concerning birth order and family size in the present study, although these factors may have substantial impacts on allergic disease susceptibility. Asthma prevalence is reportedly inversely related to family size in families with ≥4 children.30 An inverse relationship between birth order and asthma risk has also been suggested. Compared with younger siblings, stronger associations with older siblings with asthma have been demonstrated.30 However, family size was not specified in those studies; thus, there is a need to determine whether family size or birth order exerts a greater impact upon the risk of atopy. The mechanism by which younger children are protected against atopy is unknown. One possible explanation is the hygiene hypothesis, which suggests that children with less exposure to pathogens and other microorganisms in early childhood are more susceptible to allergic diseases. An implication is that the attempt to create dust-free and pathogen-free clean environment leads to increased atopy prevalence. The presence of older siblings and larger family size is presumed to protect children from atopy through greater exposure in early childhood, thus modulating their immune systems.

Univariate analysis showed that food sensitisation, but not aeroallergen sensitisation, was significantly associated with a positive BCT result in patients with AD (P=0.027). The association was not statistically significant following regression analysis. It has been reported that 40% of patients with food allergy, but no diagnosis of asthma, have a substantial degree of bronchial hyperactivity (measured by the BCT).31 Another small study (n=22 patients with allergic asthma) showed no relationship between skin prick test sensitisation and inhaled reactivity (measured by the methacholine BCT).32 Skin allergen sensitisation does not accurately predict airway allergen response.32 33 This result was confirmed by several other studies,34 35 which showed no relationship between methacholine responsiveness and the presence or degree of atopy. Hence, food and aeroallergen sensitisation are generally not associated with BCT results.

Univariate analysis showed significant associations of serum IgE level (P=0.045) and blood eosinophil count (P=0.017) with a positive BCT result. These findings were consistent with the results published by Liu et al36 concerning significant relationships of BHR to methacholine and increased total serum IgE to a positive BCT result (P=0.001). Sears et al37 showed that BHR was related to serum IgE level in children not diagnosed with asthma; this relationship persisted despite the exclusion of children with a history of AR or AD. Hence, BHR is dependent on serum IgE level and is unrelated to the presence of AD. Nevertheless, IgE can be measured in young children when BHR is difficult to demonstrate; notably, IgE is a simple blood marker of AD severity and asthma risk.7 38

The “one airway” hypothesis (ie, “united airway disease”) is based on the bidirectional interaction between asthma and rhinitis, with the implication that both upper and lower airways should be treated for optimal symptomatic control.39 40 However, our study showed no association between the presence of AR and a positive BCT result in children with AD (P=0.079). Although several studies have shown an association between AR and BHR, they did not equate a positive BCT result with the diagnosis of AR.20 41 42

In our study, there was no association between AD severity (based on objective SCORAD score, SH, and TEWL) and a positive BCT result. Liu et al36 found that BHR to methacholine was related to atopy (P=0.0063), while the degree of BHR was not significantly associated with the severity of any atopic disease.

The strengths of this study included collection and review of the data over 10 years, which enabled the addition of follow-up assessments for many of the patients. The Prince of Wales Hospital is a public hospital; the family cost of healthcare service is relatively low, which supports a low dropout rate and consistent long-term follow-up. Our relatively large sample size enabled examination of various atopic phenotypes. Patients with AD who exhibited both skin and airway manifestations confirm the presumed atopic march with progression from AD to AR and asthma, or co-expression of asthma and AD phenotypes (ie, skin sensitivity plus wheeze).

The primary limitation of the present study was that data were missing for some factors, notably family atopic conditions and laboratory tests. Regarding the family history, many parents did not provide clear information concerning their own atopic conditions. Those with mild symptoms may fail to seek medical advice, although they reported self-diagnosed atopic conditions. Although only physician-diagnosed conditions were included in the data analysis, there was difficulty confirming the validity of those family histories. A substantial number of patients were only children in their families and had no siblings. Additionally, the BCT is a medical test that provokes airway narrowing. It is physically demanding and can cause severe discomfort (eg, violent coughing) which makes the measurement difficult. The irritating nature of the BCT makes it suitable solely for older children and causes high failure rates; thus, the number of patients with a positive BCT result was relatively low. Our observations concerning the usefulness of the BCT should be confirmed in a prospective study.

In patients with paediatric AD, a positive BCT result was independently and positively associated with personal history of asthma and sibling history of atopy, but not with any other clinical parameters.

Concept or design: KL Hon, AHY Ng, CCC Chan, PXY Ho, EPM Tsoi, TF Leung.
Acquisition of data: AHY Ng, CCC Chan, PXY Ho, EPM Tsoi.
Analysis or interpretation of data: KL Hon, AHY Ng, CCC Chan, PXY Ho, EPM Tsoi, KYC Tsang.
Drafting of the manuscript: KL Hon, AHY Ng, CCC Chan, PXY Ho, EPM Tsoi, FW Ko.
Critical revision of the manuscript for important intellectual content: KL Hon, FW Ko, TF Leung.

As the editor of the journal, KL Hon was not involved in the peer review process. Other authors have disclosed no conflicts of interest.

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

This study was approved by The Joint Chinese University of Hong Kong–New Territories East Cluster Clinical Research Ethics Committee (The Joint CUHK-NTEC CREC).

1. Hon KL, Liu M, Zee B. Airway disease and environmental aeroallergens in eczematics approaching adulthood. Pediatr Respirol Crit Care Med 2017;1:81-5. Crossref

2. Hon KL, Wang SS, Leung TF. The atopic march: from skin to the airways. Iran J Allergy Asthma Immunol 2012;11:73-7.

3. Hon KL, Yong V, Leung TF. Research statistics in atopic eczema: what disease is this? Ital J Pediatr 2012;38:26. Crossref

4. Coates AL, Wanger J, Cockcroft DW, et al. ERS technical standard on bronchial challenge testing: general considerations and performance of methacholine challenge tests. Eur Respir J 2017;49:1601526. Crossref

5. Dixon C. The bronchial challenge test: a new direction in asthmatic management. J Natl Med Assoc 1983;75:199-204.

6. Pepys J, Hutchcroft BJ. Bronchial provocation tests in etiologic diagnosis and analysis of asthma. Am Rev Respir Dis 1975;112:829-59.

7. Ng C, Hon KL, Kung JS, Pong NH, Leung TF, Wong CK. Hyper IgE in childhood eczema and risk of asthma in Chinese children. Molecules 2016;21:E753. Crossref

8. Miller MR, Crapo R, Hankinson J, et al. General considerations for lung function testing. Eur Respir J 2005;26:153-61. Crossref

9. Ramsdale EH, Morris MM, Roberts RS, Hargreave FE. Bronchial responsiveness to methacholine in chronic bronchitis: relationship to airflow obstruction and cold air responsiveness. Thorax 1984;39:912-8.Crossref

10. Crapo RO, Casaburi R, Coates AL, et al. Guidelines for methacholine and exercise challenge testing-1999. This official statement of the American Thoracic Society was adopted by the ATS Board of Directors, July 1999. Am J Respir Crit Care Med 2000;161:309-29. Crossref

11. Miller MR, Hankinson J, Brusasco V, et al. Standardisation of spirometry. Eur Respir J 2005;26:319-38.Crossref

12. Spector SL, Farr RS. A comparison of methacholine and histamine inhalations in asthmatics. J Allergy Clin Immunol 1975;56:308-16. Crossref

13. Schulze J, Smith HJ, Fuchs J, et al. Methacholine challenge in young children as evaluated by spirometry and impulse oscillometry. Respir Med 2012;106:627-34. Crossref

14. Hon KL, Kung JS, Tsang KY, Yu JW, Cheng NS, Leung TF. Do we need another symptom score for childhood eczema? J Dermatolog Treat 2018;29:510-4. Crossref

15. Severity scoring of atopic dermatitis: the SCORAD index. Consensus Report of the European Task Force on Atopic Dermatitis [editorial]. Dermatology 1993;186:23-31. Crossref

16. Hon KL, Wong KY, Leung TF, Chow CM, Ng PC. Comparison of skin hydration evaluation sites and correlations among skin hydration, transepidermal water loss, SCORAD index, Nottingham eczema severity score, and quality of life in patients with atopic dermatitis. Am J Clin Dermatol 2008;9:45-50. Crossref

17. Rothe T, Spagnolo P, Bridevaux PO, et al. Diagnosis and management of asthma—the Swiss guidelines. Respiration 2018;95:364-80. Crossref

18. Cockcroft DW. Direct challenge tests: Airway hyperresponsiveness in asthma: its measurement and clinical significance. Chest 2010;138(2 Suppl):18S-24S. Crossref

19. Huang SJ, Lin LL, Chen LC, et al. Prevalence of airway hyperresponsiveness and its seasonal variation in children with asthma. Pediatr Neonatol 201;59:561-6. Crossref

20. Davis BE, Cockcroft DW. Past, present and future uses of methacholine testing. Expert Rev Respir Med 2012;6:321-9. Crossref

21. Pols DH, Wartna JB, van Alphen EI, et al. Interrelationships between atopic disorders in children: a meta-analysis based on ISAAC questionnaires. PLoS One 2015;10:e0131869. Crossref

22. Riiser A, Hovland V, Carlsen KH, Mowinckel P, Lødrup Carlsen KC. Does bronchial hyperresponsiveness in childhood predict active asthma in adolescence? Am J Respir Crit Care Med 2012;186:493-500. Crossref

23. Toelle BG, Xuan W, Peat JK, Marks GB. Childhood factors that predict asthma in young adulthood. Eur Respir J 2004;23:66-70. Crossref

24. Küster W, Petersen M, Christophers E, Goos M, Sterry W. A family study of atopic dermatitis. Clinical and genetic characteristics of 188 patients and 2151 family members. Arch Dermatol Res 1990;282:98-102. Crossref

25. Johnson CC, Ownby DR, Peterson EL. Parental history of atopic disease and concentration of cord blood IgE. Clin Exp Allergy 1996;26:624-9. Crossref

26. Thomsen SF, Ulrik CS, Kyvik KO, Ferreira MA, Backer V. Multivariate genetic analysis of atopy phenotypes in a selected sample of twins. Clin Exp Allergy 2006;36:1382-90. Crossref

27. Ober C, Hoffjan S. Asthma genetics 2006: the long and winding road to gene discovery. Genes Immun 2006;7:95- 100. Crossref

28. Sublett JL. The environment and risk factors for atopy. Curr Allergy Asthma Rep 2005;5:445-50.Crossref

29. Subbarao P, Mandhane PJ, Sears MR. Asthma: epidemiology, etiology and risk factors. CMAJ 2009;181:E181-90. Crossref

30. Goldberg S, Israeli E, Schwartz S, et al. Asthma prevalence, family size, and birth order. Chest 2007;131:1747-52 Crossref

31. Kivity S, Fireman E, Sade K. Bronchial hyperactivity, sputum analysis and skin prick test to inhalant allergens in patients with symptomatic food hypersensitivity. Isr Med Assoc J 2005;7:781-4.

32. Bowton DL, Fasano MB, Bass DA. Skin sensitivity to allergen does not accurately predict airway response to allergen. Ann Allergy Asthma Immunol 1998;80:207-11. Crossref

33. Turner KJ, Stewart GA, Woolcock AJ, Green W, Alpers MP. Relationship between mite densities and the prevalence of asthma: comparative studies in two populations in the Eastern Highlands of Papua New Guinea. Clin Allergy 1988;18:331-40. Crossref

34. Lúdvíksdóttir D, Janson C, Björnsson E, et al. Different airway responsiveness profiles in atopic asthma, nonatopic asthma, and Sjögren’s syndrome. BHR Study Group. Bronchial hyperresponsiveness. Allergy 2000;55:259-65.Crossref

35. Suh DI, Lee JK, Kim CK, Koh YY. Methacholine and adenosine 5’-monophosphate (AMP) responsiveness, and the presence and degree of atopy in children with asthma. Pediatr Allergy Immunol 2011;22:e101-6. Crossref

36. Liu SF, Lin MC, Chang HW. Relationship of allergic degree and PC20 level in adults with positive methacholine challenge test. Respiration 2005;72:612-6. Crossref

37. Sears MR, Burrows B, Flannery EM, Herbison GP, Hewitt CJ, Holdaway MD. Relation between airway responsiveness and serum IgE in children with asthma and in apparently normal children. N Engl J Med 1991;325:1067-71. Crossref

38. Hon KL, Lam MC, Leung TF, et al. Are age-specific high serum IgE levels associated with worse symptomatology in children with atopic dermatitis? Int J Dermatol 2007;46:1258-62. Crossref

39. Haccuria A, Van Muylem A, Malinovschi A, Doan V, Michils A. Small airways dysfunction: the link between allergic rhinitis and allergic asthma. Eur Respir J 2018;51:1701749. Crossref

40. Lluncor M, Barranco P, Amaya ED, et al. Relationship between upper airway diseases, exhaled nitric oxide, and bronchial hyperresponsiveness to methacholine. J Asthma 2019;56:53-60. Crossref

41. Shaaban R, Zureik M, Soussan D, et al. Allergic rhinitis and onset of bronchial hyperresponsiveness. Am J Respir Crit Care Med 2007;176:659-66. Crossref

42. Ciprandi G, Signori A, Cirillo I. Relationship between bronchial hyperreactivity and bronchodilation in patients with allergic rhinitis. Ann Allergy Asthma Immunol 2011;106:460-6. Crossref

Pneumonia caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), known as coronavirus disease 2019 (COVID-19), has become a pandemic.1 2 3 By 1 March 2020, a total of 87 137 cases were confirmed globally, including 79 968 in China and 7169 distributed across 58 countries outside China. On 23 January 2020, the Chinese Central Government imposed a lockdown in Wuhan and other cities in Hubei Province to isolate the epicentre of the outbreak; to the best of our knowledge, the ‘Wuhan lockdown’ represents the first lockdown of a major city in modern history.4 Subsequently, compulsory policies have been established, such as suspension of public gatherings and the requirement to wear masks.5 In addition to non-medical interventions, the scientific community is responding to this challenge by working to understand and control the disease.6 7 8 9 10 11 However, there have been limited studies regarding the clinical and radiological features of patients with COVID-19, based on multicentre, multiprovincial cohorts at the peak of the epidemic.

In this context, we retrospectively analysed 189 patients with laboratory-confirmed COVID-19, using data collected from seven hospitals in four provinces from 18 January 2020 to 3 February 2020. We compared clinical features, laboratory tests, and chest computed tomography (CT) image findings of these patients with respect to time (ie, before and after Wuhan lockdown) and space (ie, in and outside of Wuhan epidemic area); we investigated potential associations between CT findings and laboratory data. Our findings may help further understand the epidemiological characteristics of COVID-19 and improve the public health response to the epidemic; they can be used as a reference for implementing control measures in other regions or countries with increasing numbers of patients with COVID-19.

Data regarding 189 patients were obtained from the following seven hospitals: Taihe Hospital (n=59), Xiangya Hospital of Central South University (n=21), The Second Xiangya Hospital of Central South University (n=9), Wenzhou Hospital (n=76), Jinling Hospital (n=1), Nanjing Drum Tower Hospital (n=12), and Wuhan Hospital (n=11). Wenzhou is the prefecture-level city with the most confirmed cases outside Hubei Province. Symptom onset time was recorded from 31 December 2019 to 2 February 2020; patients were hospitalised from 18 January 2020 to 3 February 2020, with final follow-up for this report on 4 February 2020. Patients with suspected COVID-19 were admitted and quarantined, then diagnosed with COVID-19 in accordance with the ‘Novel Coronavirus Pneumonia Prevention and Control Program’ (sixth edition)—a patient was confirmed to have COVID-19 based on high throughput sequencing or real-time reverse-transcriptase polymerase chain reaction (RT-PCR) assays of nasal and pharyngeal swab specimens.12 Two target genes—open reading frame 1ab (ORF1ab) and nucleocapsid protein (N)—were simultaneously amplified and tested in real-time RT-PCR assays. Target 1 (ORF1ab) comprised forward primer 5’-CCCTGTGGGTTTTACACTTAA-3’, reverse primer 5’-ACGATTGTGCATCAGCTGA-3’, and the probe 5’-VIC-CCGTCTGCGGTATGTGGAAAGGTTATGG-BHQ1-3’. Target 2 (N) comprised forward primer 5’-GGGGAACTTCTCCTGCTAGAAT-3’, reverse primer 5’-CAGACATTTTGCTCTCAAGCTG-3’, and the probe 5’-FAMTTGCTGCTGCTTGACAGATT-TAMRA-3’. Real-time RT-PCR assays were conducted using a SARS-CoV-2 nucleic acid detection kit, in accordance with the manufacturer’s protocol (Shanghai BioGerm Medical Technology Company, Shanghai, China).

Epidemiological, clinical, laboratory, and radiological characteristics were obtained from electronic medical records by using data collection forms. Date of disease onset was defined as the day when symptoms were noticed. The number of days between symptom onset and date of the first positive test was recorded. Fever was defined as an axillary temperature of ≥37.5°C. Hypoxaemia was defined as 94% oxygen saturation, in accordance with respiratory department criteria. Major CT features were described using standard international nomenclature, defined by the Fleischner Society glossary and peer-reviewed literature regarding viral pneumonia. Degree of COVID-19 severity at the time of admission was defined as mild, moderate, severe, or critical, using preliminary diagnostic guidance from the National Health Commission of the People’s Republic of China. Disease was further separated into non-severe (ie, mild and moderate) and severe (ie, severe and critical) classifications for simplicity. Direct exposure history was defined as patient confirmation of a direct visit to Wuhan, China, during a particular period; close exposure history was defined as close patient contact with an individual who had confirmed or suspected COVID-19. To analyse spatiotemporal differences, patients were divided into different categories according to the start date for the Wuhan lockdown (ie, 23 January 2020) for temporal analysis or heavy epidemic province classification (eg, Hubei and Zhejiang provinces13) for spatial analysis.

Continuous variables were described as the mean (±standard deviation); categorical variables were expressed as frequency (%). All statistical analyses were conducted with R (version 3.6.2; https://www.r-project.org/), using Fisher’s exact test for categorical data and a two-sample Mann-Whitney test or Student’s t test for continuous data (as appropriate). Correlations were measured by Pearson’s correlation coefficient (ρ). Co-morbidities, signs, and symptoms that appeared in more than 10% of the patients were regarded as common co-existing medical conditions. For unadjusted comparisons, two-sided P values <0.05 were considered statistically significant. The analyses were not adjusted for multiple comparisons; thus, given the potential for type I error, the findings should be interpreted as exploratory and descriptive.

The present study included 189 patients with confirmed COVID-19 from four provinces in China, including 70 (37.0%) from Hubei (11 [5.8%] from Wuhan), 30 (15.9%) from Hunan, 76 (40.2%) from Zhejiang, and 13 (6.9%) from Jiangsu. Dates of confirmed infection by RT-PCR ranged from 18 January 2020 to 3 February 2020. The mean date of disease onset was 21 January 2020; the mean date of confirmed infection by RT-PCR was 28 January 2020. The mean duration between symptomology onset and first positive test was 6±5 days. Patients in severely affected areas (eg, Hubei and Zhejiang provinces) showed symptoms earlier than patients in other areas (Fig 1).

The overall characteristics of included patients are summarised in Table 1. The mean age was 44±14 years (range, 17-92 years); 100 patients (52.9%) were men. Of the 189 patients, 181 (95.8%) exhibited positive findings for COVID-19 in the initial RT-PCR assay; 186 patients (98.4%) had ≥1 co-existing medical condition. Fever (161 [86.1%]; two missing records), cough (113 [59.8%]), fatigue (68 [36.0%]), myalgia (35 [18.5%]), diarrhoea (25 [13.2%]), and headache (19 [10.1%]) were the most common symptoms at onset; hypertension (34 [18.0%]) was the most common co-morbidity. Less common co-morbidities included chronic obstructive pulmonary disease, chronic kidney disease, and malignancy (one patient each). Most patients (180 [95.2%]) had non-severe disease; patients with severe disease tended to be older (P=0.067) and had significantly greater breathing frequency (P=0.009) than patients with non-severe disease (online supplementary Appendix 1). Notably, fever was the primary symptom indicative of COVID-19 in patients with suspected disease during the epidemic; however, in our cohort, fever was independent of other imaging findings (data not shown).

On admission, 10 patients (5.3%) presented with hypoxaemia at the time of initial diagnosis; leukopenia was present in 31.2% of the patients, lymphocytopenia was present in 20.6%, and neutropenia was present in 13.2%. Patients with critical disease had more laboratory abnormalities than those with severe disease, including lymphocytopenia (44.4% vs 19.6%; P=0.09) and hypoxaemia (55.6% vs 2.8%; P<0.001). Approximately 91.0% of lesions exhibited subpleural distribution; 17.5% of lesions were diffusely distributed. The most common patterns on chest CT were mixed ground-glass opacity with consolidation (mGGO-C, 84.7%); 59.8% of patients had grid-like shadows and 27.5% of patients exhibited radiological manifestations of typical paving stones (Fig 2). Patients with severe disease showed more frequent involvement of multiple lobes (all P<0.05) and more frequent diffuse distribution (P=0.008), compared with patients who exhibited non-severe disease (online supplementary Appendix 1).

To evaluate the severity of respiratory damage caused by COVID-19, 26 patients (13.8%) who presented with subjective dyspnoea or objective hypoxia were selected for detailed analysis (Table 2). These 26 patients were generally older (50±16 years; P=0.013) and showed more diverse clinical symptoms (eg, cough [80.8%; P=0.033], fatigue [53.8%; P=0.068], nausea [30.8%; P<0.001], diarrhoea [34.6%; P=0.002], and abdominal pain [11.5%; P=0.017]), co-morbidities (eg, hypertension [38.5%; P=0.008]), and haematological abnormalities (eg, lymphocytopenia [38.5%; P=0.051]), compared with patients who did not exhibit dyspnoea or hypoxia. The radiological manifestations in these patients were not optimistic because all patients demonstrated multiple lesions (100%; P=0.123) and mGGO-C (100%; P=0.361); many patients had diffusely distributed lesions (42.3%; P=0.001) and grid-like shadows (80.8%; P=0.033) [Table 3]. Among nine patients with severe disease, seven (77.8%) had varying degrees of hypoxia and dyspnoea. Additionally, patients with haematological abnormalities (especially leukopenia or lymphocytopenia) showed more severe lobe involvement and tended to show diffusely distributed pulmonary lesions (online supplementary Appendix 2). Specifically, the white blood cell count was significantly negatively correlated with the numbers of lesions in left upper (ρ=-0.18, P=0.012), left lower (ρ=-0.23, P=0.002), and right lower lobes (ρ=-0.19, P=0.009).

Although there is no evidence that patients with hypertension are more susceptible to COVID-19, 18.0% of patients with confirmed disease exhibited hypertension, which was the most common clinical co-morbidity in our cohort. These patients were likely to exhibit hypoxaemia (14.7%; P=0.022); furthermore, their lung lobes were severely involved (all P<0.05) and lesions were significantly diffusely distributed (35.3%; P=0.006). Therefore, these patients require close clinical monitoring (Table 4).

In this cohort, all patients with severe disease showed mGGO-C. Paving stones, a sign of the inflammatory absorption period, and grid-like shadows, a sign of interstitial lung lesions, were significantly associated with the presence of mGGO-C (both P<0.05); thus, these radiological findings might serve as comprehensive indicators of disease severity in patients with COVID-19 (online supplementary Appendix 3). Additionally, these patients also showed unfavourable imaging findings, including multiple lesions and severe lung lobe involvement (all P≤0.001).

To further investigate the spatiotemporal differences among patients with COVID-19, we compared clinical, laboratory, and radiological characteristics of patients with respect to the start date of the Wuhan lockdown, as well as heavy epidemic province classification status (online supplementary Appendices 4 and 5). We found that patients in severely affected areas (eg, Hubei and Zhejiang provinces) demonstrated slightly higher body temperature (mean: 37.9℃ vs 37.6℃; P=0.070), more frequent fatigue (39.7% vs 23.3%, P=0.072), and more frequent dyspnoea (11.6% vs 0, P=0.041), compared with patients in other areas. Imaging findings showed more manifestations of multiple lesions (92.9% vs 78.0%, P=0.031), more severe lobe involvement, and more frequent radiological manifestations of mGGO-C (87.7% vs 74.4%, P=0.060). Additionally, after implementation of the ‘Wuhan lockdown’ policy, the symptoms of cough (51.0% vs 70.1%, P=0.012), nausea (3.9% vs 16.1%, P=0.010), and dyspnoea (2.0% vs 17.2%, P=0.001) were significantly alleviated in patients with newly confirmed COVID-19; lung lobe involvement was also dramatically improved, compared with patients who had been diagnosed prior to the start date of the lockdown.

This study assessed the epidemiological, clinical, laboratory, and imaging characteristics of 189 patients with confirmed COVID-19 from multiple hospitals and provinces; it also included spatiotemporal analysis of disease in these patients. As expected, there were more male patients than female patients in our cohort; fever, cough, and dyspnoea were the main symptoms at the time of initial diagnosis, accompanied by lymphocytopenia, hypoxaemia, and other haematological abnormalities. Furthermore, patients with severe disease showed significantly more severe lobe involvement and diffuse distribution of pulmonary lesions, consistent with the findings in previous studies.6 11 12 13 14 Reductions in the numbers of white blood cells or lymphocytes are closely associated with lobe involvement and diffuse distribution, such that a large number of inflammatory cells is consumed at pulmonary lesions in a short period; this finding is consistent with past pathological findings in patients with COVID-1915—interstitial mononuclear inflammatory infiltrates, dominated by lymphocytes, have been observed in both lungs; multinucleated syncytial cells with atypical enlarged pneumocytes (characterised by large nuclei, amphophilic granular cytoplasm, and prominent nucleoli) were identified in intra-alveolar spaces, which constituted a viral cytopathy-like change. Additionally, lymphopenia is a common laboratory finding in patients with COVID-19. A serological study16 and a pathological result15 demonstrated that patients’ interleukin-6 levels increased during the course of the disease, whereas the levels of CD4+ T cells, CD8+ T cells, and natural killer cells decreased. These findings imply that, as the disease progresses, patients begin to develop immunosuppression; lymphopenia may therefore be a key factor related to disease severity and mortality in patients with COVID-19.

Another important finding in this study was that patients with hypertension were likely to exhibit hypoxaemia, accompanied by unfavourable radiological manifestations; this was presumably because the patients included in this study were mostly middle-aged or elderly people. The reported prevalence of hypertension in China was 23.2% in adults,17 which was slightly higher than the prevalence in our cohort. In general, older people are more susceptible to COVID-19 and more likely to experience severe disease, compared with people younger than 50 years of age, because older people exhibit greater numbers of health conditions and co-morbidities. Notably, the zinc metallopeptidase angiotensin-converting enzyme 2 (ACE2)18 19—a negative regulator of the angiotensin system which affects heart function, hypertension, and diabetes—has been identified as a key receptor for SARS-CoV-2 in humans. Angiotensin-converting enzyme 2 protects against acute lung injury in several animal models of acute respiratory distress syndrome, which indicates that the renin-angiotensin system may play a critical role in the pathogenesis of acute lung injury. Thus, enhancement of ACE2 activity might be a novel approach for the treatment of acute lung failure in several diseases. Angiotensin-converting enzyme 2 receptors are widely expressed in nasal mucosa, bronchus, lung, heart, oesophagus, kidney, stomach, bladder, and ileum; importantly, the entrance of SARS-CoV-2 into cells mainly occurs through binding to ACE2. Thus, unlike other β-coronaviruses, SARS-CoV-2 replication is not limited to the upper respiratory mucosa epithelium (eg, nasal cavity and pharynx); it also occurs in the digestive tract and other organs, which partially explains the non-respiratory symptoms (eg, diarrhoea, liver damage, and kidney damage).20 Multiple affected organs cause diverse clinical manifestations and large individual differences, which lead to complex conditions. Accordingly, patients with a history of hypertension should receive closer monitoring.

Respiratory system infections end in respiratory failure or multiple organ failure.21 Similar to previous reports of patients with severe acute respiratory syndrome (SARS), some patients in the present study experienced dyspnoea and hypoxaemia during the course of COVID-19 (online supplementary Appendix 6). Notably, our patients showed greater numbers of clinical symptoms and unfavourable imaging findings. Pathologically, SARS mainly causes the formation of hyaline membranes, which result in large numbers of inflammatory exudates into the alveolar cavity, as well as patchy haemorrhage and focal necrosis; these changes lead to respiratory failure and extremely high mortality. In contrast, our patients with COVID-19 generally exhibited mGGO-C as the main imaging feature, which causes airway obstruction without obvious hyaline membrane formation; thus, ventilator support can be used to improve patient prognosis. We presume that the presence of early imaging findings indicates that proactive interventions (eg, positive pressure ventilation) are needed to enhance blood oxygen concentration.

Fever, the most common symptom at the first visit and the most commonly used indicator for COVID-19, showed no significant relationship with radiological findings in the present study, which implies that patients may show no abnormalities (eg, changes in body temperature) when obvious lesions form in the lungs. Furthermore, a recent study22 demonstrated that the sensitivity of RT-PCR for confirmation of COVID-19 is lower than the sensitivity of chest imaging scans, which also suggests that radiological examinations should be used as the primary screening method in this epidemic because of their efficiency, instead of the current approach of body temperature checks and RT-PCR assays.

Overall, the spatial distribution of the epidemic demonstrated here is consistent with the official statistics.23 The distribution of disease incidence had a clear relationship with population mobility. In particular, cities surrounding Wuhan (throughout Hubei Province) reported the vast majority of cases, followed by Wenzhou (Zhejiang Province), which has a large floating population from Wuhan. Wan et al24 and Wrapp et al25 showed that SARS-CoV-2 is more infectious than SARS-CoV. Imported cases were most common in the early period of the epidemic; symptoms then began to appear among individuals who had been in contact with the first group of infected individuals, which contributed to a rapid increase in the number of infections. The symptoms of fatigue and dyspnoea were alleviated outside severely affected areas, which implied reduction of virus potency during intergenerational transmission and early admission to hospitals. In the present study, we used the date of disease onset for analysis of affected patients. Patients in Hubei and Zhejiang provinces showed symptoms earlier and were confirmed to have COVID-19 an average of 6 days later, compared with patients in other areas; these findings coincide with the reported 14-day incubation period.26 Gradually, clinical symptoms and chest CT findings were alleviated in patients with newly confirmed COVID-19 after the beginning of the Wuhan lockdown; these changes also implied reduction of virus potency during intergenerational transmission.

In general, the radiological manifestations of COVID-19 are similar to those of SARS and Middle East respiratory syndrome (MERS), but pleural effusion is rare in patients with COVID-19 (online supplementary Appendix 6). In two previous studies,27 28 the proportions of patients with SARS and MERS who had pleural effusions were 25% (4/16) and 14.5% (8/55), whereas only one patient with COVID-19 (0.5%) had pleural effusions in our cohort. Current studies indicate that the binding forces between the SARS-CoV-2 S protein and human ACE2 are similar to (or stronger than) those between the SARS-CoV S protein and its receptor.25 Given the state of the epidemic, SARS-CoV-2 is highly infectious; its basic reproduction number (R0) is considerably greater than that of either SARS or MERS.29 The World Health Organization reported that the R0 of SARS-CoV-2 ranged from 1.4 to 2.5, whereas a study in China indicated an R0 of 3.3 to 5.530 and a study in the United States estimated an R0 of 3.77 (95% confidence interval, 3.51-4.05).31 The findings of our multicentre retrospective study demonstrate that current measures have affected the early epidemiological pattern (ie, rapid increase) because R0 is decreasing each day in China; however, considering the complexity of influencing factors, further evaluations and predictions are needed. The majority of patients with COVID-19 exhibit non-severe disease, which is an essential source of infection and a ‘blind spot’ for public health efforts; therefore, CT findings such as infiltration, nodules, and consolidation should be identified during early diagnosis. Notably, flu season is approaching rapidly; there is a need for attention to epidemiological history and condition monitoring, as well as efforts to block routes of transmission as quickly as possible.

We acknowledge some limitations in this study. First, the cohort size was relatively small, and data were not collected equally from each included province, which may have led to bias in the conclusions. Second, documentation was incomplete for some patients, given the variations in electronic database structures among participating sites and the urgent timeline for data extraction. Missing data included contact history, heart rate, respiratory rate, and body temperature. Because of the small numbers of patients for whom these data were missing, the main conclusions of this study were presumably unaffected. Third, the sizes and densities of mGGO-C were not compared among patients; thus, analysis of relationships between these characteristics and COVID-19 progression warrants investigation.

Clinical and imaging features were compared among patients with COVID-19 at the peak of epidemic in China. The findings suggest that mGGO-C, paving stones, and grid-like shadows might serve as comprehensive indicators of disease severity in these patients. Furthermore, radiological examinations may be useful as the primary screening method in this epidemic because of their efficiency, in contrast to the current approach of body temperature checks and RT-PCR assays.

Overall spatiotemporal trends were also evaluated retrospectively in this study. Patients in severely affected areas demonstrated slightly higher body temperature, more frequent fatigue, and more frequent dyspnoea. After implementation of the ‘Wuhan lockdown’ policy, cough, nausea, and dyspnoea were significantly alleviated in patients with newly confirmed COVID-19. These data indicate that the preventive measures adopted by China’s Central Government may be appropriate for planning efforts in other regions or countries with increasing numbers of infected patients.

Concept or design: Y Wang, F Yan, B Zhang, DY Zhang, and ZY Sun.
Acquisition of data: ZQ Wen, W Chen, W Chen, WH Liao, J Liu, Y Yang, JC Shi, SD Liu, F Xia, and ZH Yan.
Analysis or interpretation of data: X Lu, T Chen, and Y Wang.
Drafting of the manuscript: Y Wang, S Luo, CS Zhou, X Lu, and T Chen.
Critical revision of the manuscript for important intellectual content: Y Wang, B Zhang, DY Zhang, and Z Sun.

All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.

The authors declare no competing interests.

We thank Prof Guangming Lu (Department of Medical Imaging, Jinling Hospital, Medical School of Nanjing University, Nanjing, Jiangsu, China) for his coordination during the cross-centre data collection process. We also thank all hospital staff for their efforts in collecting the information used in this study; all patients who consented to inclusion of their data in the analysis; and all medical staff involved in patient care.

This work was supported by the National Natural Science Foundation of China (81720108022, 91649116, 81571040, 81973145), the Social Development Project of Science and Technology in Jiangsu Province (BE2016605, BE201707), the National Key R&D Program of China (2017YFC0112801), the Key Medical Talents of Jiangsu Province, the ‘13th Five-Year’ Health Promotion Project of Jiangsu Province (B.Z.2016-2020), the Jiangsu Provincial Key Medical Discipline (Laboratory) (ZDXKA2016020), the Project of the Sixth Peak of Talented People (WSN-138, BZ), the China Postdoctoral Science Foundation (2019M651805), the “Double First-Class” University project (CPU2018GY09), and Nanjing Health and Family Planning Commission (YKK17089). The funders had no role in study design, data collection, data analysis, interpretation, or writing of the report.

This study adhered to the tenets of the Declaration of Helsinki and was approved by the ethics committees of the seven hospitals (Taihe Hospital, Xiangya Hospital of Central South University, The Second Xiangya Hospital of Central South University, Wenzhou Hospital, Jinling Hospital, Nanjing Drum Tower Hospital, and Wuhan Hospital) with a unified approval number [M202003050028] led by Nanjing Drum Tower Hospital; a waiver of informed consent was granted because the study involved patients with emerging infectious diseases.

1. Silverstein WK, Stroud L, Cleghorn GE, Leis JA. First imported case of 2019 novel coronavirus in Canada, presenting as mild pneumonia. Lancet 2020;395:734. Crossref

2. Holshue ML, DeBolt C, Lindquist S, et al. First case of 2019 novel coronavirus in the United States. N Engl J Med 2020;382:929-36. Crossref

3. Pongpirul WA, Pongpirul K, Ratnarathon AC, Prasithsirikul W. Journey of a Thai taxi driver and novel coronavirus. N Engl J Med 2020;382:1067-8. Crossref

4. Lee J. Wuhan lockdown ‘unprecedented’, shows commitment to contain virus: WHO representative in China. 23 Jan 2020. Available from: https://www.reuters.com/article/us-china-health-who-idUSKBN1ZM1G9. Accessed 23 Jan 2020.

5. Chen S, Yang J, Yang W, Wang C, Bärnighausen T. COVID-19 control in China during mass population movements at New Year. Lancet 2020;395:764-6. Crossref

6. Chen N, Zhou M, Dong X, et al. Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study. Lancet 2020;395:507-13. Crossref

7. Kanne JP. Chest CT findings in 2019 novel coronavirus (2019-nCoV) infections from Wuhan, China: key points for the radiologist. Radiology 2020;295:16-7. Crossref

8. Li Q, Guan X, Wu P, et al. Early transmission dynamics in Wuhan, China, of novel coronavirus–infected pneumonia. N Engl J Med 2020;382:1199-207. Crossref

9. Ng MY, Lee EY, Yang J, et al. Imaging profile of the COVID-19 infection: radiologic findings and literature review. Radiol Cardiothorac Imaging 2020;2:e200034. Crossref

10. Wang D, Hu B, Hu C, et al. Clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus–infected pneumonia in Wuhan, China. JAMA 2020;323:1061-9. Crossref

11. Guan WJ, Ni ZY, Hu Y, et al. Clinical characteristics of coronavirus disease 2019 in China. N Engl J Med 2020;382:1708-20. Crossref

12. World Health Organization. Coronavirus disease (COVID-19) technical guidance publications. Laboratory testing for 2019 novel coronavirus (2019-nCOV) in suspected human cases. 2020. Available from: https://www.who.int/publications/i/item/10665-331501. Accessed 19 Mar 2020.

13. Wu Z, McGoogan JM. Characteristics of and important lessons from the coronavirus disease 2019 (COVID-19) outbreak in China: summary of a report of 72 314 cases from the Chinese Center for Disease Control and Prevention. JAMA 2020 Feb 24. Epub ahead of print. Crossref

14. Clinical findings in a group of patients infected with the 2019 novel coronavirus (SARS-Cov-2) outside of Wuhan, China: retrospective case series [editorial]. BMJ 2020;368:m792. Crossref

15. Xu Z, Shi L, Wang Y, et al. Pathological findings of COVID-19 associated with acute respiratory distress syndrome. Lancet Respir Med 2020;8:420-2. Crossref

16. Wan S, Yi Q, Fan S, et al. Characteristics of lymphocyte subsets and cytokines in peripheral blood of 123 hospitalized patients with 2019 novel coronavirus pneumonia (NCP). medRxiv [Preprint] 12 Feb 2020. Available from: https://doi.org/10.1101/2020.02.10.20021832. Accessed 19 Mar 2020. Crossref

17. Chen WW, Gao RL, Liu LS, et al. China cardiovascular diseases report 2015: A summary. J Geriatr Cardiol 2017;14:1-10.

18. Kuba K, Imai Y, Penninger JM. Angiotensin-converting enzyme 2 in lung diseases. Curr Opin Pharmacol 2006;6:271-6. Crossref

19. Turner AJ, Hiscox JA, Hooper NM. ACE2: from vasopeptidase to SARS virus receptor. Trends Pharmacol Sci 2004;25:291-4. Crossref

20. Huang C, Wang Y, Li X, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet 2020;395:497-506. Crossref

21. Ksiazek TG, Erdman D, Goldsmith CS, et al. A novel coronavirus associated with severe acute respiratory syndrome. N Engl J Med 2003;348:1953-66. Crossref

22. Fang Y, Zhang H, Xie J, et al. Sensitivity of chest CT for COVID-19: comparison to RT-PCR. Radiology 2020;296:E115-7. Crossref

23. National Health Commission of the People’s Republic of China. Update on COVID-19 epidemic as of 24:00 on 1 March 2020 [in Chinese]. 2020. Available from: http://www.nhc.gov.cn/xcs/yqtb/202003/5819f3e13ff6413ba05fd b45b55b66ba.shtml. Accessed 2 Mar 2020.

24. Wan Y, Shang J, Graham R, Baric RS, Li F. Receptor recognition by novel coronavirus from Wuhan: An analysis based on decade-long structural studies of SARS Coronavirus. J Virol 2020;94:e00127-20. Crossref

25. Wrapp D, Wang N, Corbett KS, et al. Cryo-EM structure of the 2019-nCoV spike in the prefusion conformation. Science 2020;367:1260-3. Crossref

26. Diagnosis and Treatment Protocol for Novel Coronavirus Pneumonia (Trial Version 7). 2020. Available from: http://www.shliangshi.com/newsshow_825.html. Accessed 3 Mar 2020.

27. Hsieh SC, Chan WP, Chien JC, et al. Radiographic appearance and clinical outcome correlates in 26 patients with severe acute respiratory syndrome. AJR Am J Roentgenol 2004;182:1119-22. Crossref

28. Das KM, Lee EY, Al Jawder SE, et al. Acute Middle East Respiratory Syndrome Coronavirus: temporal lung changes observed on the chest radiographs of 55 patients. AJR Am J Roentgenol 2015;205:W267-74. Crossref

29. Paules CI, Marston HD, Fauci AS. Coronavirus infections—more than just the common cold. JAMA. 2020 Jan 23. Epub ahead of print. Crossref

30. Zhao S, Lin Q, Ran J, et al. Preliminary estimation of the basic reproduction number of novel coronavirus (2019-nCoV) in China, from 2019 to 2020: A data-driven analysis in the early phase of the outbreak. Int J Infect Dis 2020;92:214-7. Crossref

31. Kim JY, Choe PG, Oh Y, et al. The first case of 2019 novel coronavirus pneumonia imported into Korea from Wuhan, China: implication for infection prevention and control measures. J Korean Med Sci 2020;35:e61. Crossref

Ductal carcinoma in situ (DCIS) is a premalignant disease in the breast cancer spectrum, in which cancer cells are confined within the basement membrane of the breast ductal system.1 Because of the enhanced availability of breast imaging and breast cancer awareness, the incidence of DCIS has increased over the past two decades.2 Although the incidence of invasive breast cancer has declined over the past decade, diagnoses of DCIS have continued to rise.3

Although DCIS is the earliest recognised form of breast cancer, its natural history remains largely unknown.4 5 Long-term survival studies have found that mortality of DCIS could be as low as 3% over 10 years of follow-up.6 The current gold standard treatment for DCIS is surgery, with or without radiotherapy, according to the type of surgery performed on a particular patient. To the best of our knowledge, there has been no randomised controlled trial comparing mastectomy and breast-conserving surgery in the context of DCIS treatment; however, a meta-analysis suggested that local recurrence rates were substantially lower among women treated with mastectomy.7

In recent decades, the incidence of DCIS has increased due to the widespread use of breast imaging screenings, on the basis of enhanced breast cancer awareness. As in other screening-detected disorders, there is widespread debate regarding whether DCIS is overdiagnosed and overtreated. Some clinicians have advocated a watchful-waiting strategy for DCIS, with the presumption that not all DCIS will progress to invasive cancer.8

In contrast to many developed countries, a population-based breast cancer screening programme is not available in Hong Kong. A recent study showed that DCIS is more frequently detected and treated in the private sector in Hong Kong, compared with the public health care system. Notably, DCIS is reportedly detected more frequently among patients in higher social classes due to self-initiated breast screening; more than half of these patients undergo successful treatment with breast-conserving surgery.9 Here, we present the results of long-term survival analyses based on a territory-wide breast cancer registry.

This was a retrospective analysis of a territory-wide, prospectively maintained database from the Hong Kong Cancer Registry, concerning patients diagnosed during the period from 1997 to 2006; data were censored in December 2015 for retrieval of long-term survival outcomes. The Hong Kong Cancer Registry is a population-based cancer registry managed by the Hong Kong Hospital Authority; this registry has been responsible for collecting basic demographic data, cancer site information, and cancer histology results for all patients diagnosed with cancer in all public and private medical institutions in Hong Kong since 1963. All raw data were validated by various crosschecking procedures involving the locally designed Cancer Case Audit System; they were scrutinised by multiple quality control processes, commensurate with the recommendations by the International Agency for Research on Cancer, a component of the World Health Organization. Queries and “unusual cases” were referred to a clinical oncologist for re-validation.

Institutional review board approval was not needed for this retrospective review of a breast cancer registry database. This study included all patients with DCIS who were diagnosed from 1997 to 2006. Exclusion criteria were age <30 years or ≥70 years, lobular carcinoma in situ, Paget’s disease, and co-existing invasive carcinoma (ie, diagnosed within 6 months of DCIS onset). Patients were stratified into those diagnosed from 1997 to 2001 and those diagnosed from 2002 to 2006. Five- and 10-year breast cancer–specific survival rates were evaluated; standardised mortality ratios were calculated (with reference to the general population of women in Hong Kong).

From 1997 to 2006, 1391 patients were diagnosed with DCIS and included in the Hong Kong Cancer Registry breast cancer database. In total, 449 patients were diagnosed from 1997 to 2001, while 942 patients were diagnosed from 2002 to 2006. The mean age at diagnosis was 49.2±9.2 years. Most patients (43.5%) were aged 40 to 49 years (Table 1). More than half of the patients (n=712, 51.2%) underwent mastectomy, while 399 (28.7%) underwent breast-conserving surgery. Overall, 410 patients (29.5%) received adjuvant radiotherapy. In addition, 221 patients (15.9%) received risk-reducing hormonal therapy with tamoxifen (Table 1).

The median follow-up interval was 11.6 years; overall breast cancer–specific mortality rates were 0.3% and 0.9% after 5 and 10 years of follow-up, respectively (Table 2). In total, 109 patients (7.8%) developed invasive breast cancer after a considerable delay. Invasive breast cancer rates were comparable between patients diagnosed from 1997 to 2001 and those diagnosed from 2002 to 2006: 37 (8.2%) and 72 (7.6%), respectively (Table 1).

Subgroup analysis revealed higher breast cancer–specific mortality in patients with human epidermal growth factor receptor 2 (HER2)–positive DCIS after 10 years of follow-up, compared with patients who exhibited HER2-negative DCIS (2.9% vs 0%; P=0.0181, Fisher’s exact test). In contrast, 10-year breast cancer–specific mortality rates were comparable between patients with low-/intermediate-grade DCIS and those with high-grade DCIS (0.5% vs 0.8%; P=0.6776).

The breast cancer–specific mortality rate (per 100 000) was 2.2 among patients aged 30 to 34 years; this rate slowly increased and peaked at 34.8 among patients aged 60 to 64 years (Table 3). Patients with DCIS were more likely to die of breast cancer, compared with the general population of women in Hong Kong (standardised mortality ratio=5.7; 95% confidence interval=3.1-8.3).

Breast cancer is the most common cancer among women in Hong Kong, such that it constituted 26.1% of all newly diagnosed cancers among women in Hong Kong in 2015.10 Notably, a population-wide breast cancer screening programme is not available in Hong Kong. However, because of improved patient-level and population-level education regarding breast cancer awareness, rates of self-initiated breast cancer screening by ultrasonography and mammography have increased over the past decade.9 This might well explain the doubling of DCIS incidence from 449 patients (1997-2001) to 942 patients (2002-2006).

The mortality rate of patients with DCIS has substantially declined over the past few decades in the United States: the 10-year breast cancer mortality rate was 3.4% for women who received a diagnosis from 1978 to 1983, then decreased to 1.9% for women who received a diagnosis from 1984 to 198911 and 1.1% for women who received a diagnosis from 1988 to 2011.2 The mortality rate of patients with DCIS in Hong Kong has remained stable during this same period, despite improved detection through selfinitiated breast screening. Nevertheless, the 10-year breast cancer–specific mortality rate of 0.9% in the current study is comparable with the findings from Western nations; in particular, the 10-year breast cancer–specific mortality rate was reportedly 1.8% in a randomised trial of 1046 Swedish patients with DCIS, who were diagnosed from 1987 to 1999.12 The underlying reason for such an improvement in survival is beyond the scope of this study, but we presume that it is multifactorial (eg, earlier detection and improved surgical oncologic treatment for DCIS).13 However, reports on the improved survival of patients with DCIS (including the current cohort) should be interpreted with care, because this improvement may be the result of overdiagnosis of DCIS.

Overdiagnosis and overtreatment for DCIS have been a major focus of debate over the past decade.12 Several randomised controlled trials, such as the COMET (NCT02926911) and LORIS trials, are currently investigating the feasibility and non-inferiority of active surveillance with or without endocrine therapy for management of low-risk DCIS.

Biological markers such as HER2 receptor and oestrogen receptor statuses have been used for assessment of prognosis and tumour behaviour in patients with invasive breast cancers,14 but their roles in the context of DCIS may have been previously underestimated. Human epidermal growth factor receptor 2–positive DCIS is considered the most unstable precursor among all molecular subtypes, because of its high invasion rate and frequent association with a discordant phenotype.15 Our results may provide clinical validation of this postulation, because they demonstrated that the 10-year breast cancer–specific mortality is significantly worse in patients with HER2-positive disease. However, because of the relatively small number of events included in the subgroup analysis, it may be premature to conclude that positive HER2 findings are associated with adverse survival outcome. Oestrogen receptor–positive DCIS was associated with slightly lower 10-year breast cancer–specific mortality (Table 2). Indeed, the use of systemic hormonal therapy with tamoxifen in patients with oestrogen receptor–positive DCIS has been shown to reduce the risk of future invasive cancer.16

We acknowledge that this study was limited by its retrospective in nature, because all pathological diagnoses were supplied by the breast cancer database from The Hong Kong Cancer Registry. A formal pathology review might have identified patients whose diagnoses were modified from DCIS (in core biopsy) to invasive cancers (in final pathology); other diagnoses might have been modified from invasive cancers to DCIS. While some researchers reported a 17% exclusion rate after a central pathology review,17 others reported a much lower exclusion rate of 2% after secondary pathological review of patients with DCIS.18 19 20 Nevertheless, our analysis was based on a large territory-wide cancer registry. All data were maintained and validated in a consistent manner. In addition, the extended follow-up period enabled detailed long-term survival analysis for patients with DCIS.

Data from the Hong Kong Cancer Registry revealed that the incidence of DCIS doubled from the late 1990s to the early 2000s. The estimated standardised mortality ratio of patients with DCIS in Hong Kong was 5.7, compared with the general population of women in Hong Kong. Our cohort represents one of the largest DCIS cohorts in the published literature. For locations where population-wide breast cancer screening is not available, as in Hong Kong, we believe that the results of our study support further investigation of the cost-effectiveness of population-wide breast cancer screening implementation.

Concept or design: M Co, A Kwong.
Acquisition of data: A Kwong, OWK Mang, RKC Ngan, AHP Tam, KH Wong.
Analysis or interpretation of data: M Co, A Kwong, OWK Mang, AHP Tam.
Drafting of the manuscript: M Co, A Kwong.
Critical revision of the manuscript for important intellectual content: A Kwong, RKC Ngan, KH Wong.

The authors have no conflicts of interest to disclose.

We thank the Dr Ellen Li Charitable Foundation and the Kuok Foundation for their continual support in providing the staff for collection of the data to make this possible. We also thank members of the Hong Kong Breast Cancer Research group for their advice on the research during the period of data collection.

This research was funded by the Dr Ellen Li Charitable Foundation and the Kuok Foundation. The funders had no role in the design of this study, the analysis and interpretation of the data, or the decision to submit the results for publication.

This study was approved by the Hong Kong Hospital Authority West Cluster Research Ethics Committee (Ref UW 09-045). Patient consent was obtained for data collection and analysis.

1. Silverstein MJ, Baril NB. In situ carcinoma of the breast. In: Donegan WL, Spratt JS, editors. Cancer of the Breast. 5th ed. Saunders: Philadelphia; 2002.

2. Ernster VL, Barclay J, Kerlikowske K, Grady D, Henderson C. Incidence of and treatment for ductal carcinoma in situ of the breast. JAMA 1996;275:913-8. Crossref

3. Surveillance, epidemiology and end results program, National Cancer Institute. USA government. Previous version: SEER cancer statistics review, 1975-2009. Available from: https://seer.cancer.gov/archive/csr/1975_2009_pops09/. Accessed 10 Jan 2019.

4. Sprague BL, Trentham-Dietz A. In situ breast cancer. In: Li CI, editor. Breast Cancer Epidemiology. New York: Springer; 2010: 47-72. Crossref

5. Allegra CJ, Aberle DR, Ganschow P, et al. National Institutes of Health State-of-the-Science Conference Statement: Diagnosis and Management of Ductal Carcinoma in Situ September 22-24, 2009. J Natl Cancer Inst 2010;102:161-9. Crossref

6. Co M, Kwong A. Ductal carcinoma in situ of the breast—long term results from a twenty-year cohort. Cancer Treat Res Commun 2018;14:17-20. Crossref

7. Boyages J, Delaney G, Taylor R. Predictors of local recurrence after treatment of ductal carcinoma in situ: a meta-analysis. Cancer 1999;85:616-28. Crossref

8. Merrill AL, Esserman L, Morrow M. Clinical decisions. Ductal carcinoma in situ. N Engl J Med 2016;374:390-2. Crossref

9. Yau TK, Chan A, Cheung PS. Ductal carcinoma in situ of breast: detection and treatment pattern in Hong Kong. Hong Kong Med J 2017;23:19-27. Crossref

10. Centre for Health Protection, Department of Health, Hong Kong SAR Government. Breast Cancer. Available from: https://www.chp.gov.hk/en/healthtopics/content/25/53.html. Accessed 7 Jul 2018.

11. Ernster VL, Barclay J, Kerlikowske K, Wilkie H, Ballard-Barbash R. Mortality among women with ductal carcinoma in situ of the breast in the population-based surveillance, epidemiology and end results program. Arch Intern Med 2000;160:953-8. Crossref

12. Early Breast Cancer Trialists’ Collaborative Group (EBCTCG), Correa C, McGale P, et al. Overview of the randomized trials of radiotherapy in ductal carcinoma in situ of the breast. J Natl Cancer Inst Monogr 2010;2010:162-77. Crossref

13. Co M, Kwong A, Shek T. Factors affecting the underdiagnosis of atypical ductal hyperplasia diagnosed by core needle biopsies—a 10-year retrospective study and review of the literature. Intl J Surg 2018;49:27-31. Crossref

14. Perou CM, Sørlie T, Eisen MB, et al. Molecular portraits of human breast tumours. Nature 2000;406:747-52. Crossref

15. Harada S, Mick R, Roses RE, et al. The significance of HER-2/neu receptor positivity and immunophenotype in ductal carcinoma in situ with early invasive disease. J Surg Oncol 2011;104:458-65. Crossref

16. Boughey JC, Gonzalez RJ, Bonner E, Kuerer HM. Current treatment and clinical trial developments for ductal carcinoma in situ of the breast. Oncologist 2007;12:1276-87. Crossref

17. Collins LC, Achacoso N, Haque R, et al. Risk factors for non-invasive and invasive local recurrence in patients with ductal carcinoma in situ. Breast Cancer Res Treat 2013;139:453-60. Crossref

18. Bijker N, Peterse JL, Duchateau L, et al. Risk factors for recurrence and metastasis after breast-conserving therapy for ductal carcinoma-in-situ: analysis of European Organization for Research and Treatment of Cancer Trial 10853. J Clin Oncol 2001;19:2263-71. Crossref

19. Fisher ER, Costantino J, Fisher B, et al. Pathologic findings from the National Surgical Adjuvant Breast Project (NSABP) Protocol B-17. Five-year observations concerning lobular carcinoma in situ. Cancer 1996;78:1403-16. Crossref

20. Rakovitch E, Mihai A, Pignol JP, et al. Is expert breast pathology assessment necessary for the management of ductal carcinoma in situ? Breast Cancer Res Treat 2004;87:265-72. Crossref

With the increasing use of screening mammography and advances in neoadjuvant therapy, tumours at the time of surgery are more often non-palpable.1 2 3 4 5 6 7 Accurate image-guided localisation is the key to successful excision of these lesions.

Hookwire localisation has been the traditional standard method of localising non-palpable breast lesions for decades. It has many inherent limitations and challenges. Wire placement has to be done on the day of surgery to minimise the risk of wire dislodgment, which limits the flexibility of radiology appointments and scheduling of surgery, therefore potentially resulting in delayed surgery.8 Wire displacement and wire transection with retained fragments have also been reported.5 9 10 The track of the wire limits the surgical approach, causing additional healthy breast tissue to be dissected along the course of the wire.5 9 10 These can affect cosmetic outcome.5 9 10

More recently, radioguided occult lesion localisation (ROLL) has gained popularity, as it overcomes many disadvantages of wire localisation and is reported to be equally effective compared to hookwire.11 However, it also needs to be performed on the same day or a day before surgery due to the half-life of the radiotracer.12 Moreover, radiation safety precautions and the need of Nuclear Medicine unit support limit its widespread use.

Recently, non-radioactive non-wire techniques have started to emerge and address many of these issues. A magnetic marker system (Magseed, Endomagnetics, Cambridge, United Kingdom) is one of these techniques and received clearance for longterm breast implantation from United States Food and Drug Administration in February 2018. It was introduced in Hong Kong in 2019. Our study aimed to evaluate the efficacy and safety of magnetic seed marker localisation of non-palpable breast lesions. To the best of our knowledge, there is no prior publication on magnetic seed marker localisation in a Chinese population.

A retrospective review of all Chinese women who underwent magnetic seed marker localisation for non-palpable breast lesions from June 2019 to February 2020 in a single institution was conducted. Patients were selected by breast surgeons and breast radiologists in consensus by reviewing images on the basis of target visibility and target depth. Patients who had a magnetic seed marker placed but surgery performed out of the study period were excluded.

The magnetic seed marker (Magseed, Endomagnetics, Cambridge, United Kingdom) is made of non-radioactive paramagnetic low-nickel stainless steel. The seed is 5 mm × 0.9 mm, which is the smallest non-wire non-radioactive localisation device available. The magnetic seed marker is preloaded in a sterile 7- or 12-cm 18-gauge deployment needle.

The magnetic seed marker is intended to be placed at a depth up to 3 cm from the skin according to the manufacturer’s instructions13 due to limitations of signal transmission from a greater depth. It is localised with a detector probe (Sentimag, Endomagnetics), which generates an alternating magnetic field to transiently magnetise the seed.14 A visual numerical value and audio feedback are produced according to the strength of the magnetic field, thus signalling the distance of the seed from the detector probe.14

Magnetic seed marker placement was percutaneously performed under image guidance by one of four breast radiologists with 3 to 19 years of experience performing image-guided breast localisation, or by a breast radiology trainee who was directly supervised by one of the breast radiologists. During ultrasound-guided placement, the patient lies supine and rolled slightly with a wedge put under the shoulder on the ipsilateral side to spread the breast evenly. The ipsilateral arm is raised over the patient’s head to facilitate a larger sterilisation field. During stereotactically guided placement, the patient lies on either side or sits up to facilitate breast compression by the stereotactic table.

Target-to-seed distance was evaluated in real time for magnetic seed markers placed under sonographic guidance and was measured on post-procedure mammograms in mediolateral and craniocaudal projections for magnetic seed markers placed under stereotactic guidance. If multiple magnetic seed markers were placed in one breast, the minimum distance between the markers was measured. For patients with magnetic seed markers inserted before the day of surgery, target ultrasound and/or mammography were performed on the day of surgery to evaluate for any delayed magnetic seed marker migration, which was defined by any difference between the initial target-to-seed distance after the localisation procedure and the final target-to-seed distance on the day of surgery. If the final target-to-seed distance was >=10 mm, signifying significant migration, alternative localisation was performed on the day of surgery. Lesions with acceptable marker position underwent marker-guided excision as planned with the depth of the marker from the skin evaluated by preoperative ultrasound, followed by intraoperative guidance with the use of the probe. The presence of the markers in the specimens was confirmed with the probe by surgeons and by specimen radiographs with the radial margins evaluated.

Rates of placement success and retrieval success with a 95% confidence interval (CI) were calculated using the Wilson score method.15 Placement success was defined as a final target-to-seed distance <10 mm in any plane on images on the day of surgery, with reference to guidelines from the National Health Service Breast Screening Programme16 and previous studies.14 17 For degrees of magnetic seed marker placement success, the final target-to-seed distances were further subdivided into ≤1 mm, 2 to 5 mm, and 5 to 9 mm. Retrieval success was determined by the presence of the magnetic seed marker(s) in the specimen radiograph.

Electronic patient records were reviewed for patients’ demographics, preoperative pathology (if any), and indications for surgery. Specimen radiographs and pathology reports were reviewed to verify excision of target lesions and to evaluate the resection margins.

The target lesions were divided into two groups according to the indications for surgery. The surgery was considered to be of therapeutic intent if the target lesion had been proven to be malignant from preoperative pathology. Otherwise, the surgery was considered to be of diagnostic intent. Among the surgeries with therapeutic intent, margin clearance, defined as at least 1-mm disease-free margins, was assessed. The re-excision rate due to inadequate margin clearance was analysed. Complications related to magnetic seed marker deployment and surgeries were recorded.

There were 22 Chinese patients with magnetic seed markers placed during the study period; one patient was excluded due to deferred surgery out of the study period (Fig 1a). A total of 21 patients, with mean age 60.0 years (range, 38-73 years) were included (Table 1). Thirteen patients (61.9%) each had one magnetic seed marker placed on the day of surgery, which were performed during the initial learning period of this new technique. Eight patients (38.1%) had nine magnetic seed markers inserted before the day of surgery in out-patient setting, ranging from 6 to 56 days from surgery with a median of 8 days (interquartile range=6.25-13.75) [Fig 1b]. Fifteen out of 22 magnetic seed markers (68.2%) were placed under ultrasound guidance, and seven magnetic seed markers (31.8%) were placed under stereotactic guidance. The most common type of target lesion was a solid mass (15 of 21, 71.4%), all of which had markers placed under ultrasound guidance. The other six lesions had magnetic seed markers placed by stereotactic guidance, including three groups of microcalcifications, one biopsy marker, one architectural distortion, and one focal asymmetry. One group of calcifications required two magnetic seed markers for bracketing due to its extensive distribution.

Two magnetic markers (9.1%) migrated >=10 mm away from their targets. Both had been placed under stereotactic guidance and migrated along the direction of breast compression (Fig 2). One of these magnetic seed markers was aimed for bracketing initially. No delayed migration was detected in all of the nine magnetic seed markers placed before the day of surgery, and there was no further migration of the two with initial migration. Among the 22 magnetic seed markers, 17 (77.3%) and three (13.6%) were ≤1 mm and 2 to 5 mm from their target, respectively (Figs 3 and 4). Therefore, placement success was achieved in 20 out of 22 magnetic seed markers, with a success rate of 90.9% (95% CI=72.2%-97.5%). The mean final target-to-seed distance was 3.1±9.8 mm (Table 2). The final distance between the two bracketing magnetic seed markers was 29 mm. All 22 magnetic seed markers were able to be localised by the probe intraoperatively and removed successfully (100%; 95% CI=85.1%-100%).

Two out of 21 lesions (9.5%) required alternative localisation performed on the day of surgery to guide lesion excision due to significant magnetic seed marker migration of >=10 mm. One of the lesions was a mammographic architectural distortion that could be visualised on ultrasound. The magnetic seed marker had migrated 13 mm laterally on mammogram. Ultrasound-guided skin marking was performed on the day of surgery with the magnetic seed marker detected and removed together with successful removal of the target lesion (Fig 2). Another lesion was a wide distribution of microcalcifications that required two magnetic seed markers for bracketing under stereotactic guidance. One of the magnetic seed markers migrated 45 mm along the direction of breast compression, with no significant associated haematoma. Salvage hookwire localisation was performed on the day of surgery. The target lesion and the non-migrated magnetic seed marker were first removed by hookwire guidance, and the migrated magnetic seed marker was then detected by the probe and removed.

Nineteen lesions (90.5%) had magnetic seed marker–guided excision as planned, with sonographic depth of the magnetic seed markers from skin ranging from 3 to 21 mm with a mean of 10.8±4.8 mm. Among these 19 lesions, 16 (84.2%) were excised with diagnostic intent and three (15.8%) were excised with therapeutic intent.

For the 16 lesions excised with diagnostic intent, preoperative biopsies or fine needle aspiration had been performed in 14 (87.5%) lesions. Core needle biopsy of 12 lesions, resulted in two with non-diagnostic findings, four with benign pathologies and six with high-risk findings; including four papillary lesions, one atypical ductal hyperplasia, and one with scanty atypical ductal cells. Fine needle aspiration was performed in two lesions, detecting one fibroadenoma and one papillary lesion. In final surgical pathology, two of these 16 lesions (12.5%) had a malignant upgrade from the core biopsy findings including one low-grade and one high-grade ductal carcinoma in situ (DCIS).

For the three lesions excised with therapeutic intent, both preoperative biopsy and final surgical pathology showed DCIS. The subtype of these lesions included a high-grade DCIS, a low-grade DCIS, and an intermediate-grade DCIS with atypical lobular hyperplasia. One of them had close (0.5 mm) margins and required re-excision, for a margin clearance rate of 66.7% and a re-excision rate of 33.3%. There were no reported complications related to magnetic seed marker localisation or lesion excision.

Successful localisation of breast lesions by magnetic seed markers was achieved in 19 out of 21 (90.5%) Chinese patients with a high placement success rate (90.9%) in our study. The majority of the magnetic seed markers were accurately placed with a mean final target-to-seed distance of 3.1 mm. All of the successfully placed magnetic seed markers were <5 mm of the target, with 85% of them ≤1 mm. In all, 100% marker retrieval was achieved without any reported complications. Such results were similar to several recent studies which revealed 100% successful magnetic seed marker retrieval14 17 18 19 20 and high placement success (96.7%-100%).14 17 18 Our re-excision rate for therapeutic intent surgery was found to be 33.3%, which was apparently higher than that reported in previous studies, ranging from 14.8% to 21.9%.17 18 19 This could be attributable to our small sample size with only three lesions excised for therapeutic intent. In fact, a prospective non-randomised control study by Zacharioudakis et al19 with 100 patients in each arm demonstrated that the outcome of magnetic seed marker localisation was comparable to hookwire localisation for breast conservation surgery in terms of re-excision rate. A systemic review by Fusco et al21 demonstrated that the successful localisation and margin clearance rates were 65% to 100% and 58% to 84%, respectively for hookwire localisation, and 93% to 100% and 60% to 100%, respectively for ROLL, while the margin clearance rates from other previous studies9 10 22 ranged from 57% to 87.4% for hookwire localisation and 75% to 93.5% for ROLL. All these suggest that magnetic seed marker is a feasible alternative localisation method.

Thirteen magnetic seed markers (59.1%) were placed on the day of surgery during our initial experience. The purpose was to ensure safety and to allow radiologists’ and surgeons’ familiarisation with the new device and workflow. Among all of the nine magnetic seed markers placed before the day of surgery (range, 6-56 d), none of them showed delayed migration on the day of surgery. This illustrates that delayed migration is unlikely to occur and it may not be necessary for patients to come back to the Radiology Department on the day of surgery to confirm magnetic seed marker position prior to the operation. Similar results were reported by a multi-centre open-label cohort study on mastectomy patients, which showed no migration of magnetic seed markers between placement and surgery, which were up to 30 days apart.20 This reassures the feasibility of decoupling of surgery and radiology appointments, which can potentially reduce localisation-related delay in surgery. Prolonged fasting before surgery and the associated increased risk of vasovagal syncope can therefore be avoided.9 Magnetic seed markers are approved to be placed up to 30 days prior to surgery in Hong Kong at the time this article was written. However, successful retrieval was achieved in one of our patients who had had her surgery deferred to 56 days after magnetic seed marker placement due to personal reasons. This suggests that magnetic seed markers may be applicable for long-term implantation, which has already been approved in the United States and Europe.

Due to limitations of signal transmission, magnetic seed markers are intended to be placed at a depth up to 3 cm from skin according to the manufacturer’s instructions.13 It is challenging to estimate the true lesion depth as the intraoperative breast position varies from the position during breast examinations, particularly when the breast is under compression during mammographic examinations. The distance from skin on the image does not necessarily reflect the shortest distance to the lesion and can be overestimated. Therefore, for lesions visible only on mammography, we selected those near the skin or at middle depth on mammography. For ultrasound-detected lesions, the sonographic depth of the lesion from the skin would be measured. We performed sonographic measurements for magnetic seed marker depth for all patients as the sonographic breast position should best resemble its intraoperative position. In our study, the depth of magnetic seed marker placement in successfully localised lesions ranged from 3 to 21 mm with a mean of 10.8 mm. All magnetic seed markers were able to be localised by the probe intraoperatively. The depth limitation of magnetic seed markers is probably not a major issue in the Chinese population, since Chinese females tend to have thinner breasts.23 Further study is warranted to validate this postulation.

Because of potential signal interference, two magnetic seed markers should not be placed at close proximity (<2 cm apart) within the breast.14 20 This can potentially limit its use in bracketing a target or in localising multiple target lesions in one breast. We had one case requiring two magnetic seed markers placed in the same breast for bracketing a group of microcalcifications. Although one of them showed significant migration from the initial target, the final distance between the two magnetic seed markers was 29 mm. Since there could be potential interference to the probe from hookwires, the target lesion and the non-migrated magnetic seed marker were first removed by hookwire guidance, and the migrated magnetic seed marker was then detected by the probe and removed. The utility of multiple magnetic seed markers in one breast should be further evaluated in future studies with larger sample sizes.

In our study, two magnetic seed markers (9.1%) were found to have undergone significant migration of >=10 mm from the target on post-insertion images. Both of them migrated along the direction of breast compression after the compression was released, with no significant hematoma detected radiologically or clinically. We postulate such migration to be resulting from the accordion effect, which is a well-known cause for clip migration after stereotactically guided biopsy. Fatty breasts are known to be more susceptible to accordion effect–related migration as they are more compressible and are usually compressed to a greater degree.24 The migrated biopsy marker can move in the direction of compression either proximal or distal to the needle track when the breast expands to its original size and shape after compression.25 26 27 28 It is best evaluated in the plane orthogonal to the direction of compression used.25 Such migration was also recognised in 5.9% of tomosynthesis-guided magnetic seed marker localisation procedures by a previous study.17 For prevention, it is suggested to hold and release the breast slowly from the compression pad after marker placement.17 Chinese patients probably have a lower risk of accordion effect–related migration, as they tend to have denser breasts.23 However, it could not be analysed in our study given our small sample size with only seven magnetic seed markers placed under stereotactic guidance. Future research with a larger sample size is needed to evaluate the association between breast density and seed migration.

There are several other drawbacks of magnetic seed marker localisation. Cost is a major concern as it is more expensive compared with hookwire or ROLL. Extra costs are needed for the initial purchase of the probes and instruments,17 as specialised non-ferromagnetic surgical instruments must be used to avoid magnetic interaction between magnetic seed marker and sensor. However, minimising localisation-related delay in surgery may reduce the operational cost and improve workflow efficiency. A full cost analysis is necessary in the future. In addition, magnetic seed markers could not be placed under magnetic resonance imaging (MRI) guidance as the deployment needle is made of stainless steel. Magnetic seed marker insertion is contra-indicated for patients who have pacemakers or implanted cardiac devices due to interference of the devices with the probe.29 Magnetic seed markers are not officially indicated for use in nickel allergy patients. Bone wax, which is used as a terminal plug in the deployment needle, contains beeswax, and may cause allergic or foreign body reaction.13 Magnetic seed marker deployment is also not advised in a patient who may undergo future breast MRI prior to surgery due to its void artefact of 4 to 6 cm distance,5 9 which influences the MRI diagnostic accuracy.5

There are several limitations to this study. It is a single-institution retrospective study without direct comparison to our hookwire localisation or ROLL cases. Patients were selected for magnetic seed marker localisation in a multidisciplinary meeting involving breast radiologists and breast surgeons and this might introduce selection bias. We did not have any patients with a preoperative diagnosis of invasive carcinoma in our study, as sentinel node and occult lesion localisation with a radioisotope still remains the preferred localisation method for invasive carcinoma requiring sentinel lymph node biopsy in our centre. This can be performed in one single procedure instead of two, thus minimising patients’ discomfort and potential complications from the procedure. However, magnetic seed markers have been reported to be a safe and feasible method for image-guided excision of invasive carcinoma.14 17 18 As discussed before, our small sample size limited our analyses of migration and margin clearance rates, and the evaluation of the feasibility of using multiple seeds in one breast for bracketing a lesion or for localising multiple lesions. A prospective randomised trial with larger sample size will be necessary to fully compare wire localisation and ROLL to magnetic seed marker localisation. Patient satisfaction, the reproducibility operator dependence of magnetic seed marker deployment and intraoperative localisation, specimen weight, and cosmetic outcome can also be investigated in future studies.

The magnetic seed marker system demonstrated safety and efficacy in Chinese women to localise and excise non-palpable breast lesions and appears to overcome many of the limitations of conventional localisation techniques. It can be an alternative to hookwires or ROLL in selected patients. Future research is needed to validate the results.

Concept or design: WY Fung, T Wong, CM Chau, ELM Yu.
Acquisition of data: WY Fung.
Analysis or interpretation of data: WY Fung, T Wong, CM Chau, ELM Yu, JKF Ma.
Drafting of the manuscript: WY Fung, T Wong, CM Chau, ELM Yu.
Critical revision of the manuscript for important intellectual content: All authors.

All authors have disclosed no conflicts of interest.

We would like to express our gratitude to our breast team (Department of Surgery, Princess Margaret Hospital) for support of our research project.

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

This study was approved by Kowloon West Cluster Research Ethics Committee (Ref 146-11). The need for patient consent was waived by the Research Ethics Committee.

1. Lui CY, Lam HS, Chan LK, et al. Opportunistic breast cancer screening in Hong Kong; a revisit of the Kwong Wah Hospital experience. Hong Kong Med J 2007;13:106- 13.

2. Lau SS, Cheung PS, Wong TT, Ma MK, Kwan WH. Comparison of clinical and pathological characteristics between screen-detected and self-detected breast cancers: a Hong Kong study. Hong Kong Med J 2016;22:202-9. Crossref

3. Welch HG, Prorok PC, O’Malley AJ, Kramer BS. Breast-cancer tumor size, overdiagnosis, and mammography screening effectiveness. N Engl J Med 2016;375:1438-47. Crossref

4. Ramos M, Díez JC, Ramos T, Ruano R, Sancho M, González-Orús JM. Intraoperative ultrasound in conservative surgery for non-palpable breast cancer after neoadjuvant chemotherapy. Int J Surg 2014;12:572-7. Crossref

5. Hayes MK. Update on preoperative breast localization. Radiol Clin North Am 2017;55:591-603. Crossref

6. Chu TY, Lui CY, Hung WK, Kei SK, Choi CL, Lam HS. Localisation of occult breast lesion: a comparative analysis of hookwire and radioguided procedures. Hong Kong Med J 2010;16:367-72.

7. Dauphine C, Reicher JJ, Reicher MA, Gondusky C, Khalkhali I, Kim M. A prospective clinical study to evaluate the safety and performance of wireless localization of nonpalpable breast lesions using radiofrequency identification technology. AJR Am J Roentgenol 2015;204:W720-3. Crossref

8. Sharek D, Zuley ML, Zhang JY, Soran A, Ahrendt GM, Ganott MA. Radioactive seed localization versus wire localization for lumpectomies: a comparison of outcomes. AJR Am J Roentgenol 2015;204:872-7. Crossref

9. Kapoor MM, Patel MM, Scoggins ME. The wire and beyond: recent advances in breast imaging preoperative needle localization. Radiographics 2019;39:1886-906. Crossref

10. Cheang E, Ha R, Thornton CM, Mango VL. Innovations in image-guided preoperative breast lesion localization. Br J Radiol 2018;91:20170740. Crossref

11. Ocal K, Dag A, Turkmenoglu O, Gunay EC, Yucel E, Duce MN. Radioguided occult lesion localization versus wire-guided localization for non-palpable breast lesions: randomized controlled trial. Clinics (Sao Paulo) 2011;66:1003-7. Crossref

12. Manca G, Mazzarri S, Rubello D, et al. Radioguided occult lesion localization: technical procedures and clinical applications. Clin Nucl Med 2017;42:e498-e503. Crossref

13. Endomag Ltd. Magseed® magnetic marker system: Instructions for use. 2017. Available from: https://www. endomag.com/magseed/overview/. Accessed 30 Mar 2020.

14. Price ER, Khoury AL, Esserman LJ, Joe BN, Alvarado MD. Initial clinical experience with an inducible magnetic seed system for preoperative breast lesion localization. AJR Am J Roentgenol 2018;210:913-7. Crossref

15. Wilson EB. Probable inference, the law of succession, and statistical inference. J Am Stat Assoc 1927;22:209-12. Crossref

16. Sibbering M, Watkins R, Winstanley J, Patnick J, editors. Quality Assurance Guideline for Surgeons in Breast Cancer Screening (NHSBSP Publication No. 20). 4th ed. Sheffield: NHS Cancer Screening Programmes; 2009.

17. Lamb LR, Bahl M, Specht MC, D’Alessandro HA, Lehman CD. Evaluation of a nonradioactive magnetic marker wireless localization program. AJR Am J Roentgenol 2018;211:940-5. Crossref

18. Thekkinkattil D, Kaushik M, Hoosein MM, et al. A prospective, single-arm, multicentre clinical evaluation of a new localisation technique using non-radioactive Magseeds for surgery of clinically occult breast lesions. Clin Radiol 2019;74:974.e7-11. Crossref

19. Zacharioudakis K, Down S, Bholah Z, et al. Is the future magnetic? Magseed localisation for non palpable breast cancer. A multi-centre non randomised control study. Eur J Surg Oncol 2019;45:2016-21. Crossref

20. Harvey JR, Lim Y, Murphy J, et al. Safety and feasibility of breast lesion localization using magnetic seeds (Magseed): a multi-centre, open-label cohort study. Breast Cancer Res Treat 2018;169:531-6. Crossref

21. Fusco R, Petrillo A, Catalano O, et al. Procedures for location of non-palpable breast lesions: a systematic review for the radiologist. Breast Cancer 2014;21:522-31. Crossref

22. Nadeem R, Chagla LS, Harris O, et al. Occult breast lesions: a comparison between radioguided occult lesion localisation (ROLL) vs. wire-guided lumpectomy (WGL). Breast 2005;14:283-9. Crossref

23. Maskarinec G, Meng L, Ursin G. Ethnic differences in mammographic densities. Int J Epidemiol 2001;30:959-65. Crossref

24. Rosen LE, Vo TT. Metallic clip deployment during stereotactic breast biopsy: Retrospective analysis. Radiology 2001;218:510-6. Crossref

25. Burbank F, Forcier N. Tissue marking clip for stereotactic breast biopsy: initial placement accuracy, long-term stability, and usefulness as a guide for wire localization. Radiology 1997;205:407-15. Crossref

26. Liberman L, Dershaw DD, Morris EA, Abramson AF, Thornton CM, Rosen PP. Clip placement after stereotactic vacuum-assisted breast biopsy. Radiology 1997;205:417-22. Crossref

27. Esserman LE, Cura MA, DaCosta D. Recognizing pitfalls in early and late migration of clip markers after imaging-guided directional vacuum-assisted biopsy. Radiographics 2004;24:147-56. Crossref

28. Endomag Ltd. Sentimag®: instructions for use. 2018. Available from: https://www.endomag.com/sentimag/. Accessed 30 Mar 2020.