RESUMEN
Purpose: Hepatitis B surface Antigen (HBsAg) is the hallmark in diagnosing hepatitis B virus (HBV) infection. In India many commercial assays are available for detection of HBsAg but very few can measure it quantitatively. The present study presents the comparative evaluation of two methods and their correlation with serum HBsAg in chronic hepatitis B (CHB) patients. Materials and Methods: Consecutive patients of CHB were included and there HBsAg levels were measured by two methods: (i) Elecsys, Roche Diagnostics, a qualitative assay and (ii) Architect, Abbott Diagnostics, a quantitative assay. The HBV DNA was measured by real-time polymerase chain reaction (qPCR). Results: Total of 136 patients were included in the study and there was a signifi cant overall correlation between both the assays (correlation coeffi cient [r] = 0.83; P < 0.001). Assays correlated well with each other across all subgroups of CHB: treatment naïve (r = 0.73; P < 0.001, n = 32), on treatment (r = 0.56; P < 0.05, n = 104), hepatitis Be (HBe) antigen positive (r = 0.67; P < 0.001, n = 62) and anti-HBe positive (r = 0.61; P < 0.05, n = 74) group. On correlation with serum HBV DNA, Architect assay demonstrated good correlation (r = 0.73; P < 0.001, n = 136) as compared to the Elecsys assay (r = 0.27; P = 0.068, n = 136). Architect HBsAg QT assay (A1) also correlated well with HBV DNA in the treatment naïve group (r = 0.69; P < 0.001, n = 32). Conclusions: Our study hence proved that both the assays are comparable and a simple qualitative assay with in-house modifi cation can be used easily for quatitation of HBsAg in clinical samples.
RESUMEN
BACKGROUND: The Elecsys hepatitis B surface antigen (HBsAg) II quantitative assay is a newly introduced electrochemiluminescence immunoassay incorporating an initial 1:400 onboard dilution and a simple algorithm to determine HBsAg levels in serum. We evaluated the performance of the Elecsys HBsAg II assay and determined the impact of its initial onboard dilution on laboratory efficiency. METHODS: HBsAg levels were determined using both Roche Elecsys and Abbott Architect HBsAg assays. Linearity and precision of the Elecsys HBsAg II assay and its correlation with the Architect HBsAg assay were evaluated. In particular, precision was verified at Samsung Medical Center, Severance Hospital, Seoul St. Mary's Hospital in Seoul, using the same pooled serum controls. The efficiency of the dilution algorithm for both methods was verified using data from 1,848 clinical samples. RESULTS: The Elecsys HBsAg II assay showed a good linearity from 0.1 to 48,000.0 IU/mL and a good correlation (r=0.9998) between expected and measured values. Precision analyses performed at Samsung Medical Center, Severance Hospital, Seoul St. Mary's Hospital showed excellent performance with coefficients of variation between 1.28% and 6.82%. The values of the Elecsys HBsAg II and Architect HBsAg assays were well correlated (n=506, r=0.987, P<0.001) and also reliably determined in hepatitis C virus- and hepatitis B virus-co-infected patient sera (n=27). In terms of efficiency, 64.0% of samples provided a final HBsAg result on the first run without the need for further dilution, when using the 1:400 onboard pre-dilution protocol of the Elecsys HBsAg II assay. CONCLUSIONS: Given the excellent precision and correlation with the Architect assay, the Elecsys HBsAg II assay showed a potential advantage for laboratory efficiency by significantly reducing the need for retesting samples with high HBsAg levels.