"Single step" PCR with a sensitivity similar to nested PCR for the detection of hepatitis C virus RNA.

Objective: Evaluation of the performance of different HCV PCR detection systems for HCV RNA: A nested PCR, considered the reference assay, was compared with two single-step methods (ss-PCR): the first is based on the detection of PCR products by liquid hybridization with a 32P end-labelled probe (isotopic ss-PCR), while the second assay is a colorimetric method (colorimetric ss-PCR) using microwell plate hybridization with a specific nucleic acid probe (Amplicor HCV PCR, Roche Diagnostics Systems).

Methods: Sera from 56 patients with suspected hepatitis C infection based on reactive serology or altered liver parameters, and sera from 15 blood donors were tested for HCV RNA: After RNA extraction, the synthesized HCV cDNA was amplified in parallel using isotopic ss-PCR, colorimetric ss-PCR and nested PCR. The products were detected by autoradiography, color development and ethidium bromide fluorescence, respectively.

Results: In order to assess the analytical sensitivity of ss-PCR versus that of nested of PCR, experiments included serial dilutions of positive control samples. Results showed that both methods had an extinction signal at the 1:512 dilution. A comparative analysis of 71 clinical sera samples was obtained using the three protocols and the results clearly documented 100% concordance.

Conclusions: Single step PCR methods for HCV RNA have a sensitivity equal to that of nested PCR and appear more suitable for diagnostic applications. Ss-PCR is safer than nested PCR in terms of both specificity and contamination problems. In particular, the Roche Amplicor HCV PCR assay minimizes sample exposure and management problems.