Outcome of thyroid gene expression classifier testing in clinical practice.

OBJECTIVES/HYPOTHESIS Gene expression classifiers can safely reduce diagnostic thyroid surgery for fine-needle aspiration cytology (FNAC) indeterminate thyroid nodules. STUDY DESIGN Retrospective review, single-institution, single-practice surgeon. METHODS Three-year retrospective review of indeterminate FNAC that went on to gene expression classifier testing. RESULTS A total of 520 patients met American Thyroid Association guideline criteria for surgeon-performed ultrasound-guided FNAC for a thyroid nodule with on-site cytopathology. The indeterminate (Bethesda III or IV) FNAC rate was 9%. Prevalence of malignancy in FNAC indeterminate was 21%. Thirty-two cases went on to gene expression classifier testing. Fourteen were benign, 15 suspicious, and three with no result. CONCLUSIONS Benign gene expression classifier testing had an estimated negative predictive value of 100% during the study period. These patients have been observed for a mean and median duration of 14 and 7 months, respectively. In this small series, 14 of 29 patients with indeterminate FNAC were spared diagnostic surgery. LEVEL OF EVIDENCE 4.