Hong Kong Med J 2009;15:90-3 | Number 2, April 2009
Clinical significance of Trichomonas vaginalis detected in Papanicolaou smear: a survey in female Social Hygiene Clinic
Steven KF Loo, William YM Tang, KK Lo
Tuen Mun Social Hygiene Clinic, Centre for Health Protection, Department of Health, 5/F, Tuen Mun Eye Centre, Tuen Mun, Hong Kong
OBJECTIVES. To evaluate the clinical significance of Trichomonas vaginalis detected in Papanicolaou (Pap) smears in our local population.
DESIGN. Retrospective study.
SETTING. A sexually transmitted disease clinic in Hong Kong.
PATIENTS. All patients having Pap smear, wet mount microscopy, and high vaginal swab culture performed in Tuen Mun Social Hygiene Clinic from April 2005 to December 2006 were recruited.
MAIN OUTCOME MEASURES. Sensitivity, specificity, positive and negative predictive values of the Pap smear for the diagnosis of Trichomonas vaginalis.
RESULTS. A total of 209 patients had the diagnosis of Trichomonas vaginalis in the study period. From among these, the results of 149 patients who had Pap smears, wet mount microscopy, and high vaginal swab culture performed were used in the analysis. Sixty cases were excluded because treatments were initiated before the consultation or because the Pap smear had not been done. Among the Trichomonas vaginalis cases with positive Pap smears, 58% (85/146) were symptomatic and 41% (60/146) had concomitant sexually transmitted disease. The respective sensitivity and specificity of the Pap smear in our study were: 98% (128/131; 95% confidence interval, 94-100%) and 96% (440/458; 94-98%). In total, 128 patients were defined as true positives by wet mount microscopy or culture, while 18 were defined as false positives. In our study population, the positive predictive value was 88% (128/146; 95% confidence interval, 82-93%). On comparing the clinical features of patients with true-positive and false-positive Pap smears, the odds ratio for the presence of symptoms and concomitant sexually transmitted disease was 1.9 (95% confidence interval, 0.7-5.1) and 2.0 (0.7-5.8), respectively. There were no statistically significant differences in the univariate analysis by Chi squared testing.
CONCLUSION. Treatment for vaginal trichomoniasis is recommended if Trichomonas vaginalis is detected in a Pap smear.
Key words: Sensitivity and specificity; Sexually transmitted diseases; Trichomonas vaginalis; Trichomonas vaginitis; Vaginal smears
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