ABSTRACT
BACKGROUND: The sensitivity of the blood screening test is crucial to ensure blood safety. Generally the test methods with greater sensitivity tend to have lower specificity. Therefore, secondary confirmatory tests are required to solve this problem. Since the confirmatory test for hepatitis B virus surface antigen (HBsAg) has not been routinely applied yet in Korea for blood donors, the true positive rate of HBsAg is unknown. This study was intended to determine the true seroprevalence of the hepatitis B virus (HBV) among Korean blood donors. METHODS: A total of 906 blood donor samples found to be positive for HBsAg with Prism qualitative assay from November 2010 to April 2011 at Korean Red Cross blood centers were tested with Architect HBsAg qualitative assay and confirmatory assay. Blood samples with negative results using Architect HBsAg qualitative assay were tested with Prism HBsAg confirmatory test. RESULTS: Of the 906 samples positive by Prism HBsAg qualitative assay, 793 were confirmed as positives. The positive predictive value of Prism HBsAg qualitative assay was 87.5%, and the true seroprevalence of HBV among Korean blood donors was 8 out of 100,000. The sample-to-cut-off ratio (S/CO) value of one true positive sample was lower than 1. CONCLUSION: The positive predictive value of HBsAg by Prism was higher than expected. Baseline data for estimation of residual risk of HBV as well as the cost-effectiveness analysis for lookback policy were drawn. Finally, the current cut-off level for repeat assay looked reasonable and it should be maintained at least until the nucleic acid amplification test is implemented as a routine screening method.