Improvement of the Accuracy of Hepatitis B Surface Antigen Testing Using a Confirmatory Test

Abstract

Background: The hepatitis B surface antigen (HBsAg) is one of the most important serologic markers in diagnosing hepatitis B virus infection. As more sensitive immunoassays become available, the false positive rate of HBsAg has been increasing. Therefore, it has been suggested that a standardized HBsAg testing strategy be implemented to maximize the accuracy and minimize cost and complexity. This study evaluated HBsAg confirmatory tests and the HBsAg testing process to reduce false-positive HBsAg results, and the financial and time burden of the laboratory. Methods: Samples with Elecsys HBsAg II (Roche Diagnostics, Germany) cutoff index (COI) 0.9–50.0 and Alinity i HBsAg (Abbott, Ireland) signal-to-cutoff (S/CO) 1.0–30.0 were analyzed with the Elecsys HBsAg confirmatory test (Roche Diagnostics) and the Alinity i HBsAg qualitative II confirmatory test (Abbott), respectively. Results: The Elecsys and Alinity confirmatory tests were positive in 94.0% (47/50) and 69.4% (25/36) of tested samples, respectively. HBsAg COI results were significantly higher in the confirmatory test positive group than the confirmatory test negative group (Elecsys HBsAg median COI 1.20 vs. 4.38 [P =0.024] and Alinity HBsAg median S/CO 1.36 vs. 4.65 [P =0.000]). HBsAg test specificity was 100% with Elecsys COI 1.3 and Alinity S/CO 2.9. Conclusions: The HBsAg value which is likely to be positive in the neutralization test, differed depending on the patient population and reagents. By performing a neutralization test for weakly positive samples below the cutoff and adapting a single serological test strategy for samples above the cutoff, we expected to decrease false-positive results, with less time and effort.