Comparison of two quantitative hepatitis C virus reverse transcriptase PCR assays.

A quantitative hepatitis C virus reverse transcriptase PCR (HCV RT-PCR) assay established in our laboratory was compared with the Roche Amplicor HCV Monitor test kit for agreement of test results and intra-assay variability. Both assays rely on reverse transcription and amplification of extracted RNA from patients' sera together with an internal RNA standard derived from the 5'-noncoding region of HCV. A panel of clinical serum samples (n = 33) was quantitatively analyzed in parallel by both test systems. The methods demonstrated substantial agreement between 1 x 10(3) and 5 x 10(5) HCV RNA molecules per ml of serum. However, with sera containing more than 5 x 10(5) copies per ml, according to our in-house assay, the results diverged on average in a nonacceptable range of 2 orders of magnitude. Our in-house HCV RT-PCR assay measured up to 5 x 10(7) HCV-RNA molecules per ml in some serum samples. However, the Roche Amplicor HCV Monitor test kit did not detect more than 2 x 10(6) molecules in any of the serum samples tested. After dilution of serum samples prior to testing, an approximately 0.5 order of magnitude more HCV RNA molecules was detected by the Roche HCV test kit in sera containing high copy numbers (> 5 x 10(5) RNA copies according to the in-house assay). The in-house PCR and the Roche Amplicor HCV Monitor test kit revealed coefficients of variation of 6.2 and 7.5%, respectively.