Quantitative measurement of HCV RNA in the serum: A comparison of three assays based on different principles

Abstract

Quantitative measurement of hepatitis C virus (HCV) RNA is useful in patients with chronic hepatitis C, especially with interferon treatment. We examined the clinical usefulness of the AMPLICOR monitor assay, a newly developed assay for quantitative measurement, by comparing it with two other assays with different principles. A total of 48 patients with chronic hepatitis C who were treated with interferon‐α (IFN‐α) were studied: 19 were complete responders and 29 were non‐responders. Hepatitis C virus RNA was measured quantitatively by AMPLICOR, branched DNA (bDNA) probe, and competitive polymerase chain reaction (C‐PCR) assays. An internal quantification standard was used in the AMPLICOR assay. A cDNA competitor with a deletion of 15 base pairs in the middle portion was used in the C‐PCR method. The concentration of HCV RNA was significantly correlated between the three assays adopted in this study. Sensitivity of assays was 100% by C‐PCR, 90% by AMPLICOR and 69% by bDNA assays. The active quantitative range was best with the C‐PCR assay and worst with the bDNA assay. The bDNA assay had a tendency to exhibit lower values for patients with serotype 2 than did the other two assays. The predictive rate of the long‐term response to IFN‐α therapy, before its initiation, was over 75% in all three assays. The predictive rate just after completing IFN‐α therapy was as high as 80% by C‐PCR and the AMPLICOR assays, but was low (58%) with the bDNA assay. The handling of the bDNA and AMPLICOR assays was much easier than the C‐PCR assay, which required time and skill. These results indicate that the AMPLICOR assay is a simple and reliable method for measuring the serum concentrations of HCV RNA, and thus is suitable for clinical application.