Ultrasonographic characteristics predictive of nondiagnostic results for fine-needle aspiration biopsies of thyroid nodules.

The objective of this study was to identify clinical and ultrasonographic (US) characteristics predictive of nondiagnostic results. An experienced radiologist performed an US-guided fine-needle aspiration biopsy (US-FNA) for 1493 thyroid nodules in 1419 patients. Cytological results were classified as nondiagnostic (<6 groups of cells containing more than 10 cells) or diagnostic. The clinical characteristics of patients and the US features of thyroid nodules were compared according to nondiagnostic or diagnostic results. Age and sex were not associated with nondiagnostic results. A cystic portion >50% and hypoechogenicity were independent factors for predicting nondiagnostic results in all nodules (odds ratios [OR] = 2.82 and 1.88, respectively). In 534 nodules with more than 50% of cystic portion, the size of more than 10 mm and in 813 solid nodules, the size of 5 mm or smaller increased the likelihood of nondiagnostic results (ORs = 3.61 and 1.88, respectively).