Fine-needle aspiration cytology of the thyroid: screening or diagnostic test?

�It is difficult to compare the two studies due to the exclusion of follicular tumours from their statistical analysis. Unlike FNAC of other organs, FNAC of the thyroid should be regarded as a screening test to determine whether a patient needs surgery rather than a diagnostic test, though some cases can be confidently diagnosed as carcinoma on FNAC. Since all lesions with a cytological diagnosis of follicular and Hurthle cell lesions would be operated on to exclude malignancy, their reason for excluding these is difficult to understand. If their cases were classified as non-neoplastic (hyperplastic nodules, thyroiditis, etc) or neoplastic (adenoma, carcinoma), as in our study, the sensitivity, specificity, positive predictive value, and negative predictive value would be 97.6%, 48.1%, 75.4%, and 92.6% respectively compared with 56%, 90%, 74%, and 80% in our study. Many factors are responsible for the widely differing results reported by