Proposal of efficient workflows for confirmatory neutralization test for initial hepatitis B surface antigen positive samples

Background: Since more sensitive immunoassays have been introduced, false positive Hepatitis B surface antigen (HBsAg) results are increasing. This study was carried out to propose a process to reduce the burden of the laboratory while increasing positive predictive value in HBsAg. Methods: Samples with Elecsys HBsAg II (Roche Diagnostics, Germany) between cutoff index (COI) 0.9 and 10.0 were tested with Elecsys HBsAg Confirmatory Test (Roche Diagnostics). If the COI value after neutralization is less than or equal to 60% of the COI treated with control reagent, the sample was determined as HBsAg positive. Results: A total of 133 samples were analyzed and 70.7% were confirmed positive. The highest COI of negatively confirmed sample was 5.6. Receiver operating characteristic curve analysis of HBsAg assay showed an area under curve of 0.761. Specificity was 100% at COI 6.0. Conclusions: Based on this finding, the authors propose that only samples with HBsAg COI less than 6.0 need confirmatory tests.