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

Abstract

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 address the overscreening and overdiagnosis issues. This study aimed to evaluate the change in the diagnostic effectiveness of thyroid cancer screening over the last decade.

Methods: This single-center, retrospective observational study analyzed the data of 125,962 thyroid nodules obtained 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 included 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 evaluated 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.

Keywords: Diagnostic Imaging; Early Detection of Cancer; Fine-Needle Biopsy; Predictive Value of Tests; Thyroid Neoplasms.

Figure. 1.

Flowchart showing the total number of population included in the study. US, ultrasonography; FNA, fine-needle aspiration.

Figure. 2.

Pearson’s correlation coefficients were calculated to evaluate the correlation between the annual number of thyroid fine-needle aspiration (FNA) biopsy performed in patients visiting from 2010 to 2019 and (A) the annual number of thyroid cancer diagnosis confirmed through FNA biopsy, (B) the positive predictive values (PPV), and (C) the difference in PPV from previous year. The linear lines indicate significant correlations (P<0.05). *The PPV were calculated. The results are shown in the fourth column of Table 1. See the commentary in Table 1 for a detailed equation. ^†Differences in PPV from that in the previous year were calculated using the following equation: difference in PPV=(number of thyroid cancer diagnoses–number of thyroid cancer diagnoses from previous year)/(number of thyroid FNA–number of thyroid FNA from previous year). The calculated annual changes can be both positive and negative.

Figure. 3.

Positive predictive values* (%) of thyroid fine-needle aspirations performed on patients visiting the health promotion center from 2010 to 2019. *Positive predictive values were calculated and shown on the fourth column of Table 1. See commentary on Table 1 for a detailed equation.