The 2020–2021 surveys on the external quality assessment scheme for serologic tests for syphilis in Korea were conducted by the Korean Association of External Quality Assessment Service. Proficiency testing panels, comprising three pooled serum samples, were shipped to 585–592 laboratories participating in the program between 2020–2021. Rates of returning results for nontreponemal and treponemal tests were 90.1% and 43.6% in the first trial of 2020, 90.5% and 43.3% in the second trial of 2020, 90.6% and 43.6% in the first trial of 2021, and 90.5% and 40.9% in the second trial of 2021, respectively. The most commonly used nontreponemal tests were the rapid plasma reagin (RPR) card test, followed by the RPR turbidimetric immunoassay. The most commonly used treponemal tests were the Treponema pallidum particle agglutination test, followed by the immunochromatographic assay, chemiluminescence immunoassay, T. pallidum latex agglutination, and fluorescent treponemal antibody absorption. Overall accuracy of qualitative nontreponemal and treponemal tests between 2020–2021 was 98.7%–100.0%, similar to 2018–2019. In contrast, accuracy of high-titer positive samples was relatively low at 80.0%–91.5% for a semi-quantitative nontreponemal test. A mainstream group used the RPR card test, and other non-mainstream groups used the Venereal Disease Research Laboratory antigen for titer. When the two groups were separated, the accuracy increased to 92.5%. Based on these data, it is recommended to perform a proficiency test by separating the two tests, especially in a nontreponemal titer test.

Keywords: External quality assessment, Proficiency testing, Serology, Syphilis