Thyroid FNA cytology: Impact of the COVID‐19 pandemic and vaccination in a Brazilian series

Background The coronavirus disease 2019 pandemic prompted changes in medical practice, with a reduction in cytopathology volumes and a relative increase in the malignancy rate during lockdown and the initial postlockdown period. To date, no study has evaluated the impact of these changes on the volume of rapid on‐site evaluation (ROSE) or on the frequency of cases according to The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) categories after vaccination. Methods Ultrasound‐guided thyroid fine‐needle aspiration (FNA) and ROSE assessments performed from January 2019 to May 2022 were evaluated retrospectively according to TBSRTC categories for three periods: prepandemic (period 1), from transmission to expansion (period 2), and after vaccination (period 3). Results There were 7531 nodules from 5815 patients. FNA cases increased throughout the pandemic despite a drop during lockdown. The frequency of TBSRTC categories changed. Nondiagnostic cases had an increase of 18.1% in period 2 and 76.2% after vaccination compared with prepandemic levels. Malignant cases increased from 2.3% to 4.2% in period 2 and to 5.1% in period 3, representing increases of 83.1% and 121.2%, respectively, compared with period 1. Data corrected by time showed increases in categories IV, V, and VI and a decrease in benign nodules during the two pandemic periods. ROSE was performed in 787 cases during the prepandemic period, and there were decreases of 29.4% and 22.8% in periods 2 and 3, respectively. The ROSE‐to‐category I ratio was reduced significantly after vaccination. Conclusions Increased volume with sustained lower benign rates and higher malignant rates before and after vaccination indicate better selection of patients for FNA. A worse adequacy rate was correlated with a decrease in the number of ROSE assessments. Increased volume of thyroid fine‐needle aspiration cases throughout the coronavirus disease 2019 pandemic, despite a sharp drop at the initial phase, coupled with a decrease in the number of cases submitted to rapid onsite evaluation, were correlated with a low adequacy rate. Gradual growth of the volume postlockdown, especially after vaccination, was sustained with a lower frequency of benign cases and higher rate of malignancy compared with the prepandemic period, thus reflecting a better selection of cases for fine‐needle aspiration and confirming a change in the authors’ practice.