RESUMO
BACKGROUND: Hepatitis B surface antigen (HBsAg) clearance during chronic hepatitis B (CHB) infection is associated with improved long-term clinical outcome, so is considered an important therapeutic goal in CHB. Studies have shown that serum HBsAg quantification during, and at end of, treatment may predict long-term HBsAg loss. OBJECTIVES: Performance comparison of the qualitative Elecsys HBsAg II assay using a quantitative research protocol and an established quantitative HBsAg assay. STUDY DESIGN: A dilution algorithm was developed for the Elecsys HBsAg II assay to allow quantification of HBsAg levels; this was used to measure HBsAg levels in a range of samples including sera from patients infected with different HBV genotypes, HBV mutants, and longitudinal samples from patients undergoing antiviral treatment. Results were compared with those from the quantitative Architect HBsAg assay. RESULTS: There was significant overall correlation between Elecsys and Architect assays (correlation coefficient [r]=0.97; p<0.001). HBsAg levels measured with both assays correlated well in all phases of infection (r=0.80-0.96), across all genotypes tested (HBV genotype A, r=0.89; HBV genotype D, r=0.97), and in samples with lamivudine-resistant mutations (r=0.94). Bland-Altman analysis showed only minor discordance between assays in different phases of chronic HBV-infection (3.8-5.1%). This strong correlation was also present for sera with lower HBsAg concentrations. On-treatment HBsAg levels were similar when measured with either assay. CONCLUSIONS: Using a simple dilution algorithm, the quantitative Elecsys HBsAg II assay reliably determined serum HBsAg levels in a wide range of samples, and showed very high correlation with the Architect HBsAg assay.
