Thyroid Ultrasound-Guided Fine-Needle Aspiration: The Positive Influence of On-Site Adequacy Assessment and Number of Needle Passes on Diagnostic Cytology Rate

Objective: Nondiagnostic cytology is the most important limitation of thyroid ultrasound-guided fine-needle aspiration (US-FNA). This study aimed to identify factors associated with the adequacy rate of thyroid US-FNA. Study Design: Consecutive thyroid US-FNAs (2006-2013) were retrospectively included. Attending radiologists, radiology fellows and radiology residents performed US-FNA, usually involving 2-3 needle passes. In more recent years, rapid on-site adequacy assessment (ROSAA) was performed to ensure specimen adequacy. US characteristics, procedural variations and cytology results were extracted from US and pathology reports and statistically evaluated. Results: Diagnostic cytology was obtained in 64.6% of 1,381 thyroid US-FNAs. Factors associated with nondiagnostic cytology were ROSAA (74.6% diagnostic cytology, OR 0.55, 95% CI 0.42-0.71), ≥3 clinic visits for US-FNA of the same thyroid nodule (54.7%, OR 1.56, 95% CI 1.16-2.10) and increased intranodular vascularization (51.8%, OR 1.73, 95% CI 1.17-2.57). With ROSAA, an increasing number of needle passes demonstrated improving adequacy rates. The adequacy rate was not operator-dependent. Conclusion: This study demonstrates that ROSAA improves the adequacy rate of thyroid US-FNA. Without ROSAA, we recommend performing at least 3 needle passes. Less diagnostic cytology is obtained from nodules with increased intranodular vascularization or from those undergoing US-FNA ≥3 times.