Second generation amplicor-HCV monitor assay: clinical features and predictors of the response to interferon

The aims of this study were to compare the amplicor-HCV monitor assay versions 1.0 and 2.0, and to investigate the clinical usefulness of this assay in patients with chronic hepatitis C. We retrospectively analyzed 154 patients, and 133 of these patients received interferon therapy. Sixty-nine patients were complete responders (CR), and 64 were non-responders. Serum HCV RNA levels of version 1.0 and version 2.0 and HCV genotypes were determined in all patients. There was a good correlation between versions 1.0 and 2.0 in both genotype 1b and 2a, 2b (r=0.907 and 0.726, respectively). In genotype 1b, the mean HCV RNA level obtained by version 1.0 was 384+/-547 kcopies/ml and that obtained by version 2.0 was 488+/-825 kI.U./ml. In genotype 2a/2b, the mean level obtained by version 1.0 was 170+/-369 kcopies/ml and that obtained by version 2.0 was 340+/-402 kI.U./ml. Discriminant analysis revealed that the discriminating points of IFN response were 168 kcopies/ml (genotype 1b, version 1.0), 106 kcopies/ml (genotype 2a and 2b, version 1.0), 102 kI.U./ml (genotype 1b, version 2.0), and 277 kI.U./ml (genotype 2a and 2b, version 2.0). When the patients were stratified according to the discriminating points, the CR rate below the discriminating points were 73.8 and 86.2% in versions 1.0 and 2.0, respectively, in genotype 1b, and the rates were 73.2 and 82.3% in genotype 2a/2b. In addition, receiver-operating characteristic analysis revealed that version 2.0 had significantly better discriminative ability in patients with genotype 1b. We conclude that the second version of the amplicor-HCV monitor assay measures HCV RNA levels with the same precision as version 1.0 and is more useful for the prediction of interferon response than version 1.0.