[Comparison of two commercial molecular assays for quantitative measurement of hepatitis B viral DNA]

The detection and quantification of hepatitis B virus (HBV) genomes appear to be the most reliable method for monitoring HBV infection and assessing responses to antiviral treatment. For quantitative determination of HBV viremia molecular biology-based assays are used. The aim of this study was to compare and evaluate the performance of two HBV DNA detection and quantification commercial assays: hybrid-capture Digene Hybrid Capture HBV DNA assays and based on competitive polymerase chain reaction (PCR) Cobas Amplicor HBV Monitor Roche Diagnostics. Reproducibility, linearity, sensitivity were determined with 2-fold dilution series of high-titers samples and with 113 sera samples from patients with chronic HBV infection. Within-run and between-run coefficients of variation ranged from 2.4-9.7% for hybrid-capture and from 3.7-15% for PCR-based Monitor. The hybrid-capture and PCR Monitor assays appeared to be linear throughout their range of quantification: 5-2000 pg/ml and 2 x 10(2)-2 x 10(5) copies/ml respectively. The HBV DNA units used in the two assays were not comparable. Hybrid-capture and Monitor gave concordant results with 87 (82.1%) of 106 samples. The assays were both positive with 79 (74.5%) samples and were negative in 7 (7.5%) cases. Hybrid-capture and Monitor gave discordant results in 17 (17.9%) cases. The Monitor Assay was positive in 13 (61.9%) of the 21 samples negative in hybrid-capture. The competitive PCR-based Monitor assay appear to be significantly more sensitive but slightly less reproducible than the hybrid-capture. In the group of patients with seroconversion to anti-HBe PCR method should be used for measurement of viral load. In the presence of HBe antigen concentration of HBV DNA may be tested by hybrid-capture assay. Also these two assays may be used in complementary fashion in the management of HBV infected patients. It seems reasonable to use a hybrid-capture assay first, because its linear range of quantification is extended to high values and to use Monitor for samples that are negative in hybrid capture, because, its significantly higher sensitivity. However the lack of standardization among the assays makes it difficult to compare the results.