Ultrasound-guided fine-needle aspiration for solid thyroid nodules larger than 10 mm: correlation between sonographic characteristics at the needle tip and nondiagnostic results.

The objective of this study was to investigate the effect of the ultrasonographic (US) characteristics and ultrasound elastography (UE) patterns on the probability of a nondiagnostic result when performing ultrasound-guided fine-needle aspiration (UG-FNA) cytological sampling of solid thyroid nodules larger than 10 mm, to determine the efficacy of needle tip localization in UG-FNA. We retrospectively reviewed the cytological results of 710 samples from 355 patients. We compared the US characteristics and UE patterns between nodules with nondiagnostic and diagnostic results, using univariate and multivariate analyses. Among the 710 samples, 81 samples (11.4 %) from 41 patients had nondiagnostic results. According to multivariate analysis, the combinations of hypoechogenicity with avascularity [odds ratio (OR) = 2.42; 95 % confidence interval (CI) 1.37-3.72; p < 0.05], hypoechogenicity with the "hard pattern" (OR = 2.12; 95 % CI 1.58-4.59; p < 0.05), and hypoechogenicity with avascularity and the hard pattern (OR = 2.61; 95 % CI 1.40-5.21; p < 0.05) were risk factors that increased the incidence of nondiagnostic results in UG-FNA. UG-FNA was more likely to yield nondiagnostic results when the needle tip sampling region displayed hypoechogenicity and avascularity in US and the hard pattern in UE.