The diagnostic value of fine-needle aspiration cytology in the assessment of thyroid nodules: a retrospective 5-year analysis

GPS Yeoh, CK Wai
Histopathology, Canossa Hospital, 1 Old Peak Road, Hong Kong

OBJECTIVE. To audit the diagnostic accuracy and value of fine-needle aspiration cytology in the assessment of thyroid nodules over a 5-year period.

DESIGN. Retrospective study.

SETTING. Private practice, Hong Kong.

PATEINTS. The computerised records from cytological and histological examinations of all thyroid specimens submitted from 1993 through 1997 were studied; the 1236 aspirates came from 1033 women and 175 men (gender was not specified in 28 cases).

MAIN OUTCOME MEASURES. Cytological reports were classified diagnostically, and histological and cytological correlations were determined.

RESULTS. Of the 1236 aspirates, 113 (9.1%) were unsatisfactory; 1013 (82.0%), including cysts, were benign; and 110 (9.0%) were neoplastic or malignant. Histological follow-up was available for 149 cases; 13 were unsatisfactory for cytological diagnosis. Statistical analysis of the remaining 136 cases yielded the following results: sensitivity of fine-needle aspiration cytology, 56%; specificity, 90%; positive predictive value, 74%; negative predictive value, 80%; accuracy, 79%. These results were within the range of previously published values. The sensitivity was improved by combining clinical information: if nodules larger than 3-cm diameter were excised (despite a non-neoplastic aspiration cytology report), the sensitivity increased to 71% and the accuracy to 84%.

CONCLUSION. Fine-needle aspiration cytology is an effective screening test to help evaluate whether surgery is required in the management of thyroid nodules. False-positive and false-negative rates can be minimised by taking clinical and imaging data into consideration.

Hong Kong Med J 1999;5:140-4

Key words: Biopsy, needle; Cytodiagnosis; Predictive value of tests; Sensitivity and specificity; Thyroid neoplasms