Predictors of Repeat Nondiagnostic Cytology in Thyroid Fine-Needle Aspiration.

INTRODUCTION: Nondiagnostic results after thyroid fine-needle aspiration (FNA) are common and may delay diagnosis. PURPOSE: To identify demographic and sonographic predictors of nondiagnostic cytology at repeat thyroid FNA and to report malignancy rates in this group. MATERIALS AND METHODS: Single-center retrospective cohort including consecutive adult patients who underwent repeat ultrasound-guided FNA of thyroid nodules with prior nondiagnostic cytology (Bethesda I) between 2015 and 2023. Nodule-level ultrasound features were extracted from structured reports. The primary outcome was nondiagnostic cytology at repeat FNA. Multivariable logistic regression with generalized estimating equations was used to account for clustering of nodules. RESULTS: A total of 208 patients with 242 thyroid nodules were included. On repeat FNA, 77 of 242 nodules (31.8%) remained nondiagnostic. In multivariable analysis, older age (odds ratio OR per year, 1.03) and nodule composition were independently associated with a nondiagnostic result at repeat FNA. Solid nodules had lower odds of a nondiagnostic result than cystic or mixed cystic-solid nodules (OR, 0.30). Patient sex, maximum diameter, echogenicity, echogenic foci, calcifications, shape, and margins showed no significant association. Cytology suspicious for or diagnostic of malignancy (Bethesda V-VI) was found in 4 nodules (1.6%); however, this estimate may be affected by verification bias. CONCLUSION: Approximately one-third of nodules remained nondiagnostic at repeat FNA. Older age and cystic or mixed nodule composition were independently associated with a higher risk of repeat nondiagnostic cytology. Alternative diagnostic strategies (eg, rapid on-site evaluation, core-needle biopsy, or surveillance) can be considered early in the diagnostic workup of these nodules.