Quantitative cytology and thyroperoxidase immunochemistry: new tools in evaluating thyroid nodules by fine-needle aspiration.

Fine-needle aspiration (FNA) of cold thyroid nodules is proposed to be the most useful diagnostic test for deciding which patients need surgery. A retrospective study of standard cytology (SC) performed in 776 patients who had been operated on, showed a sensitivity of 94% and a specificity of 80%. Quantitative cytology (QC) was carried out with a cell image analyzer, which classified the cases as benign or not benign. In 87 cases, sensitivity and specificity of QC alone were 100 and 76%. When SC and QC were combined, there were no false negative reports. A new monoclonal antithyroperoxidase (TPO) antibody (MoAb47) was tested. The sensitivity and specificity of TPO alone were 97 and 81%. When SC and TPO were combined, specificity rose 90%. As adjuncts to SC, QC and TPO represent useful tools for selecting patients for surgery.