Hepatitis C virus RNA quantitation in a nationwide French cohort of patients co-infected with HIV and HCV: should the same test be applied to all samples?

In the ANRS CO13 HEPAVIH Cohort, HCV RNA measurement was performed with one of the two available real-time PCR assays [Roche Cobas AmpliPrep-Cobas TaqMan HCV (CAP-CTM) and the Abbott Real-Time HCV (ART)], according to the assay used in each center. To comply with the recommendations for using the same assay in multicenter clinical trials, all the 204 samples analyzed with ART were retested retrospectively by CAP-CTM. The aim of this study was to assess the usefulness of this strategy in real-life situations. A significant and positive correlation was observed between HCV RNA levels measured in the same samples with ART and CAP-CTM with all the genotypes tested. However, in 33 of the 204 (16%) clinical samples, the individual difference between HCV RNA levels measured by both assays was above ±0.5 log(10)IU/ml. Such viral load variations above 0.5 log(10) should be considered as significant. HCV RNA levels estimated by CAP-CTM for genotype 4 were significantly lower than those for genotypes 1, 2, and 3 (P<0.0001). This study shows that using the same assay in multicenter trials and cohorts is still relevant due to inter-assay differences observed in HCV plasma load measurements.