2021 Volume 70 Issue 3 Pages 560-565
Occasionally, the results of initial and confirmatory hepatitis B surface antigen (HBsAg) tests are different. We defined samples both indicating 0.05 ≤ < 10 IU/mL in the initial test and finally resulting in negative results as false positives and those finally resulting in positive results as true positives. The aims of this study were to clarify the samples considered false positives, compare the initial and confirmatory test values, and compare results of HBsAg tests with those of antibody to the hepatitis B core antigen (anti-HBc) tests. In total, 12,407 samples were included in this study. One hundred and sixty-two samples indicated positivity in the initial tests. Fifty-five samples indicating 0.05 ≤ < 10 IU/mL in the initial tests were tested again after high-speed centrifugation, and 21 samples were tested with neutralization. As a result, 39 samples were found to be false positives and 16 samples were true positives. Thirty samples indicated negative conversion after high-speed centrifugation, and nine samples indicated negative conversion on neutralization. There was no significant difference in the initial test values of false positives and true positives. Anti-HBc results were obtained from seven samples. Four samples indicated negativity for both HBsAg and anti-HBc, one sample indicated positivity for both HBsAg and anti-HBc, and two samples indicated HBsAg negativity and anti-HBc positivity. In summary, false positives in HBsAg tests were found in our hospital, and we were unable to distinguish true positives from false positives among the initial test values. Therefore, we suggest that confirmatory tests should be carried out to obtain accurate results. Furthermore, anti-HBc may help identify false positives.
