As a diagnostic immunology program of the Korean Association of External Quality Assessment Service, two trials were organized to assess the external quality of hepatitis serology in 2018 and 2019. The hepatitis serology program consisted of 10 test items. For this, we delivered four kinds of pooled sera specimens to 1,068 and 1,076 institutions for external proficiency testing in 2018 and 2019, respectively. Out of the participating laboratories, 1,041 (97.5%) and 1,046 (97.9%) responded in the first and second trials of 2018, respectively. In the first and second trials of 2019, 1,058 (98.3%) and 1,057 (98.2%) participating laboratories responded. The most commonly tested items were hepatitis B surface antigen (HBsAg), followed by antibodies against hepatitis B surface antigen (anti-HBs), anti-hepatitis C virus (anti- HCV), hepatitis B envelope antigen (HBeAg), antibodies to hepatitis B envelope antigen, anti-hepatitis A virus, and antibodies to hepatitis B core antigen. The most frequently used methods for detecting viral markers were chemiluminescence immunoassay and electrochemiluminescence immunoassay. In 2019, the use of immunochromatography assay (ICA) kits for HBsAg and anti-HBs detection increased. Some ICAs showed falsenegative results for HBeAg and anti-HCV due to low sensitivity. Improved pooled sera production reduced the HBeAg false-positive rate due to the matrix effect. The quality of viral hepatitis testing should be continuously improved through participation in the survey.

Keywords: External quality assessment, Hepatitis A, Hepatitis B, Hepatitis C, Immunoassay, Laboratory proficiency testing, Pooled serum