A-326 Evaluation of a Hepatitis B Core Total Antibody Assay Eliminating the Retest Zone and Its Post-Live Performance

Background Hepatitis B virus (HBV) affects 3.3% of the global population, resulting in 1.2 million new chronic cases and 1.1 million deaths annually. Serological tests, including qualitative measurement of total anti-HBV core antibodies, are essential for diagnosing and differentiating acute, chronic, or past infections. To ensure the reliability of positive results, samples that were initially borderline positive are typically retested in duplicate, with the final result determined by consensus (2 out of 3 readings). Recently, Siemens updated its assay from HBcT, which had a retest zone of 0.50–0.99 index with a cutoff of 0.50, to HBcT2, which eliminated the retest zone and changed positivity cutoff to 1.0. We evaluated the performance of the new HBcT2 assay and monitored its post-implementation outcomes. Methods The HBcT and HBcT2 chemiluminescent immunoassays were performed on Atellica IM analyzers (Siemens, NY). The accuracy, precision, sensitivity, and specificity of the HBcT2 assay were evaluated using control materials and patient specimens. Discordant results were reviewed based on medical history and related lab data. Following HBcT2 implementation, the positive rate was analyzed for specimens tested at our medical center from September 5, 2024, to January 11, 2025. Results Assay validation results are summarized in the table. The assay specificity of HBcT and HBcT2 was 93.0% and 95.8%, respectively. Post-implementation, the HBcT2 assay showed a positive rate of 5.6% (218 of 3,862), which was not significantly different (p=0.199) from the positive rate of 5.1% (225 of 4,409) observed with the HBcT assay. Conclusion The new HBcT2 assay improved performance by eliminating the need for repeat testing and enhancing specificity.