HBsAg confirmation: an experimental test.

Background: The specificity of HBsAg testing is to be confirmed with antibody blocking to avoid false positive results.

Objective: To test the experimental HrAb HBsAg-blocking activity and to use this new antibody in the verification of repeatedly reactive HBsAg blood serum samples.

Study Design: HbsAg screening of three quality control panels was followed by a comparative confirmatory test with commercial HuAb and experimental HrAb. The HrAb was used in subsequent HBsAg confirmation trials.

Results: A good agreement in the results obtained using the two antibodies was found, independently of the type of HBsAg neutralization step performed (either preincubation or competitive inhibition). Of the 97 repeatedly reactive HBsAg blood serum samples, 79 were 'confirmed positives'. On repeated confirmations by two antibodies, 13/18 'not confirmed' converted to 'confirmed positives', while the same five samples still remained false positive.

Conclusion: The results suggest that (1) HrAb is as good as HuAb in HBsAg confirmation and (2) HBsAg confirmatory testing is essential in the laboratory examinations of the HBsAg repeatedly reactive samples.