Association Between Sonographic Calcification Phenotype and Nondiagnostic Thyroid Fine‐Needle Aspiration

Objective To determine whether sonographic calcification phenotype is associated with nondiagnostic (Bethesda I) cytology following thyroid fine‐needle aspiration (FNA). Methods This retrospective tertiary‐centre cohort included 3639 thyroid FNA records from 2393 patients between 2012 and 2026. Calcification was classified using ACR TI‐RADS echogenic‐foci categories as none, macrocalcification, peripheral/rim calcification, punctate echogenic foci or multiple calcification types. The primary outcome was Bethesda I versus Bethesda II–VI. Generalized estimating equation logistic regression accounted for clustering of multiple nodules within patients. The primary model adjusted for age, nodule size, composition and calendar year. Results Overall, 537/3639 FNAs (14.8%) were Bethesda I. Nondiagnostic rates were 13.4% without calcification, 16.5% with macrocalcification, 20.1% with rim calcification, 13.4% with punctate echogenic foci and 19.4% with multiple calcification types (overall unadjusted p = 0.015). Rim calcification was associated with higher crude odds of Bethesda I than no calcification (OR 1.63, 95% CI 1.15–2.30; p = 0.009) and remained associated after adjustment (aOR 1.45, 95% CI 1.01–2.07; p = 0.044). The effect was similar when needle‐pass number was added (aOR 1.46, 95% CI 1.01–2.10; p = 0.044). The adjusted omnibus calcification‐phenotype test was not significant ( p = 0.375). Conclusions Rim calcification showed the highest nondiagnostic rate among isolated calcification phenotypes, whereas punctate echogenic foci did not increase nondiagnostic sampling. Calcification architecture may influence FNA adequacy, although the rim‐specific association should be considered hypothesis‐generating and requires prospective validation.