Application Study of Neutralization Confirmatory Testing for Low Positive Hepatitis B Surface Antigen.

Background: The high sensitivity of HBsAg quantitative tests has led to some challenges in the qualitative interpretation of weakly positive specimens. This study aimed to explore the clinical utility of neutralization confirma-tory testing for specimens with low positive hepatitis B surface antigen (HBsAg).

Methods: A retrospective analysis was conducted on outpatient and inpatient cases, from January 2021 to January 2022, at the Zhongshan City People's Hospital, Zhongshan. Confirmatory testing as well as enzyme-linked immunosorbent assay (ELISA) was applied to reanalyze 382 samples with low positive HBsAg detected by chemilumi-nescence microparticle immunoassay (CMIA). A retrospective analysis of hepatitis B serum markers, including e-antigen, e-antibody, and core antibody patterns, was also performed.

Results: When the HBsAg value ranged from 0.05 - 0.09 IU/mL, the positivity rate of the confirmatory testing was 34.5%. The HBsAg true positivity levels were all between 0.07 and 0.09. In the range of 0.10 - 0.49, the positivity rate of confirmatory testing was 96.1%. The three methods exhibited a high consistency, when testing samples with relatively high HBsAg values. A receiver operating characteristic (ROC) analysis showed that the optimal sensitivity and specificity were achieved at 0.14 IU/mL. For the HBV e-antigen-positive and negative groups, the positivity rate of confirmatory testing was 100% and 93.8%, with no statistical difference between them.

Conclusions: For specimens with weakly positive, low-value HBsAg, particularly when the hepatitis B surface an-tigen level is less than 0.14 IU/mL, neutralization confirmatory testing can serve as a means for further confirmation.