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

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.