Comparison of HCV RNA assays for the detection and quantification of hepatitis C virus RNA levels in serum of patients with chronic hepatitis C treated with interferon.

Detection and quantification of hepatitis C virus (HCV) RNA levels by using the standardized qualitative Amplicor HCV and quantitative Amplicor HCV Monitor assays (Roche Molecular Systems) were evaluated in 48 patients with chronic hepatitis C treated with interferon. Results were compared with an in-house reverse transcription and polymerase chain reaction (RT-PCR) assay and the branched DNA (bDNA) assay (Quantiplex, version 1.0, Chiron Diagnostics). Concordance of the qualitative results with the Amplicor HCV and in-house RT-PCR assays occurred in 82% of the samples. All but one of the discrepant specimens were found positive by the Amplicor HCV assay and negative by the in-house RT-PCR. Among the samples with HCV RNA levels measurable with the Amplicor HCV Monitor assay, 22% had HCV RNA titers below the detection limit of the Quantiplex assay. A statistically significant correlation was found between the 2 quantitative assays, although lower titers were obtained with the Amplicor HCV Monitor assay. More important, a good correlation was observed in the evolution of viremia as measured by the 2 assays during interferon therapy. During follow-up of interferon treatments, with the Amplicor HCV Monitor assay, persisting viremia was still detected in 27% of the patients who normalised alanine aminotransferase (ALT), emphasizing the bioclinical relevance of the assay. Pre-treatment serum HCV RNA levels above 10(5) copies/ml were found more frequently in nonresponders than in responders (76% vs. 44%; P < 0.05). Given their great sensitivity and the significant correlations, the Amplicor HCV qualitative and quantitative assays appear useful for the diagnosis and management of hepatitis C infection, and especially for monitoring of therapy.