Evaluation of the clinical usefulness of COBAS AMPLICOR HCV MONITOR assay (ver2.0): Comparison with AMPLICOR HCV MONITOR assay (ver1.0) and HCV core protein level

The quantitation of serum levels of hepatitis C virus (HCV) RNA in chronic hepatitis C has been regarded as one of the most important indicators for the outcome of interferon (IFN) therapy. The AMPLICOR HCV MONITOR version 1.0 (AMPLICOR v1.0) assay is widely used for the evaluation of the HCV level. A new generation assay called the COBAS AMPLICOR HCV MONITOR version 2.0 (COBAS v2.0) assay, which is semiautomated and modified to amplify all genotypes equally, has been developed. The aim of this study was to evaluate the clinical relevance of the COBAS v2.0 assay in comparison with the AMPLICOR v1.0 assay and HCV core protein assay in patients with chronic hepatitis C before IFN therapy. HCV RNA was detectable in 230 cases (97.5%) and undetectable in 6 cases (2.5%) by the COBAS v2.0 assay. The RNA levels measured by the AMPLICOR v1.0 assay correlated significantly with those measured by the COBAS v2.0 assay, and the sensitivity of the new version 2.0 assay was better than that of version 1.0, especially in serotype 2. In relation to the outcome of IFN therapy, HCV RNA levels from virologically sustained responders by the AMPLICOR v1.0 assay were 82.3 +/- 22.9 kcopies/ml in serotype 1 and 36.9 +/- 13.4 kcopies/ml in serotype 2, and those from virologically nonsustained responders were 525.2 +/- 48.6 kcopies/ml in serotype 1 and 76.7 +/- 19.5 kcopies/ml in serotype 2.The rates of sustained response to <100 kcopies/ml were 34/63 (54.0%) in serotype 1 and 24/48 (50.0%) in serotype 2. A statistically significant virological response was seen in serotype 1 (P < 0.0001), but not in serotype 2. In contrast, the levels in virologically sustained responders by the COBAS v2.0 assay were 88.2 +/- 20.5 KIU/ml in serotype 1 and 136.8 +/- 40.1 KIU/ml in serotype 2, and those in virologically nonsustained responders were 608.8 +/- 48.4 KIU/ml in serotype 1 and 328.3 +/- 62.8 KIU/ml in serotype 2. The rates of sustained response to <100 KIU/ml were 33/60 (55.0%) in serotype 1 and 21/35 (60.0%) in serotype 2. Statistical significance in virological response was seen in both serotype 1 (P < 0.0001) and serotype 2 (P < 0.05). Although the sensitivity of the HCV core protein assay was lower than that with the COBAS v2.0 assay, the HCV core protein levels also correlated well with the results of the COBAS v2.0 assay. The HCV core protein levels of virologically sustained responders were 37.6 +/- 12.0 pg/ml in serotype 1, 81.3 +/- 37.0 pg/ml in serotype 2, and those of virologically nonsustained responders were 289.9 +/- 23.5 pg/ml in serotype 1, 191.4 +/- 32.1 pg/ml in serotype 2. This assay could predict the outcome of IFN therapy in both serotype 1 (P < 0.0001) and serotype 2 (P < 0.05). Thus, both the COBAS v2.0 assay and the HCV core protein assay showed that the viral load was an indicator of virologically sustained response in serotype 2 and in serotype 1.