LAUSR

OBJECTIVES The first Bethesda classification category of thyroid fine-needle aspiration biopsy (FNAB) is nondiagnostic (ND), which indicates that the specimen's cellularity is inadequate for evaluation. This work investigated the effect of needle diameter size on ND rates by comparing diagnostic outcomes of FNAB samples collected with 23-, 25-, and 27-gauge needles. METHODS This was a retrospective analysis of samples collected from patients undergoing FNAB between 2018 and 2021. It was conducted in an otolaryngology department in a university teaching hospital. RESULTS Of the 699 aspirations, 144, 335, and 220 were performed using 23-, 25-, and 27-gauge needles, respectively. ND rates increased significantly when using 27-gauge compared with 23- to 25-gauge needles (P = .002), and a significantly lower ND rate was found for the 25-gauge needle compared with the 27-gauge needle (P = .001). Furthermore, increased nodule size was associated with reduced ND rate (odds ratio, 0.801; 95% confidence interval, 0.691-0.929). CONCLUSIONS The 25-gauge needles are superior to 27-gauge needles in reducing ND rates of thyroid nodule FNAB specimens. Future prospective studies should be performed to confirm these findings.