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

To determine whether sonographic calcification phenotype is associated with nondiagnostic (Bethesda I) cytology following thyroid fine-needle aspiration (FNA).

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.

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).

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.