Changes in Diagnostic Performance of Thyroid Cancer Screening before and after the Korean Thyroid Imaging Reporting and Data System Revision

Background: Since the era of "thyroid cancer epidemic," many Korean academic societies discouraged the use of ultrasonography in healthy individuals and revised the Korean Thyroid Imaging Reporting and Data System to ad-dress the overscreening and overdiagnosis issues. This study aimed to evaluate the change in the diagnostic effec-tiveness of thyroid cancer screening over the last decade. Methods: This single-center, retrospective observational study analyzed the data of 125,962 thyroid nodules ob-tained during cancer screening at the health promotion center of Seoul National University Bundang Hospital from 2010 to 2019. Only 327 thyroid cancer cases pathologically confirmed by fine-needle aspiration (FNA) were includ-ed in the study. The strength of the association between the number of FNA and (1) the number of thyroid cancer diagnoses, (2) the positive predictive values (PPVs), and (3) the difference in PPV from the previous year were eval-uated using Pearson's correlation analysis. Results: The number of thyroid FNA biopsies as well as the thyroid cancer diagnoses decreased from 2010 to 2019 (166 to 48 [-71.1%] vs. 43 to 22 [-48.8%]). The PPV of FNA biopsies increased from 25.9% to 45.8% (+76.8%) and was negatively correlated with the number of FNA biopsies performed (R=-0.87, P<0.001). The difference in PPV from the previous year increased similarly but without statistical significance (R=-0.59, P=0.09). Conclusion: The diagnostic efficiency of thyroid cancer screening has increased over the last decade, as evidenced by the increasing PPV of FNA biopsies.