Nevertheless, some viable quasispecies are clinically relevant and contribute, for example, to antiviral resistance. Viral load monitoring allows clinicians to modify therapy depending on the response, which is partly determined by these mutations. Against this background, Roche has been in the forefront of developing combined therapeutic and diagnostic systems. For example, Roche's Amplicor HCV , one of a number of their proprietary diagnostic systems is the 'most sensitive test' for circulating HCV-RNA in serum, plasma and to monitor patients' response to antiviral therapy. So, clinicians could use the quantitative Amplicor HCV assay to assess viral load and genotype.
Patients then undergo treatment stratified according to the viral load response.
For example, patients with undetectable viral load continue treatment. Those subjects who do not show a decline in viral load will end treatment. Patients with intermediate responses receive either dose modifications or combination therapy. In many cases, interferon is combined with another antiviral, ribavirin. There is little doubt that the approach is effective.