Abstract

Interpreting quantitative HBV, HCV and HIV-1 nucleic acid testing

Author(s): ManojK.Rajput

Monitoring ofHBV,HCVandHIV-infected individualswhich are on antiviral treatment, ideally requires periodic viral load measurements to track legitimate response to treatment. Quantification of viral load has greatly improved the monitoring of therapies for infected individuals. There are several commercially available assays for the quantitation of HBV, HCV and HIV-1 load, but still the viral load could not be presented accurately for the initiation of antiviral therapy and follow up therapy. The objective of this study is to provide information for interpretation of viral load data of an infected patient for selection of an appropriate molecular assay for initiation and follow up of antiviral therapy. Twenty nucleic acid positive plasma samples each ofHBV, HCV,HIV-1were used in the study.The same molecular assay in subsequent run showedup to 0.2-log10variations and different assays showed up to 0.4-log10viral load variations for the same set of samples. The large range of variations were observed in samples having higher viral loads (>one million copies/ml). Several times it has been observed that the viral load results of >100 copies/ml aremore reliable in comparison to low viral load results. The molecular assays of different manufacturers showed sizeable differences in viral loads for samples having HBV genotype A in comparison to HBV genotype D.The factors like clinically relevant cut-off, natural variability of viral load, the inherent variability of viral load assays, inter and intra assay variations, precision, linear range of an assay should benormalised beforedetermining the effectiveness of an antiviral therapy