Comparison between three quantitative assays in patients with chronic hepatitis C and their relevance in the prediction of response to therapy

To compare three quantitative assays measuring viral load in patients with chronic hepatitis C and to determine their value in predicting response to interferon (IFN) therapy, we analysed serum from 896 patients from eight Eu ropean Centres using QUANTIPLEX(TM) bDNA, MONITOR AMPLICOR(TM) and SUPERQUA NT(TM) assays. Analyses were performed on the same sample. Viral genotype w as assessed using INNO-LiPA HCV II kits. Intercentre variations were observ ed that were related to the handling of specimens not processed and stored within 6 h of blood sampling. Among sera with optimal handling, a stronger correlation was observed between bDNA and SUPERQUANT (0.806) than between b DNA and MONITOR (0.677) and between MONITOR and SUPERQUANT (0.632). These d iscrepancies were greatest with genotype 2 (bDNA/SUPERQUANT= 0.772; bDNA/MO NITOR=0.456; SUPERQUANT/MONITOR= 0.299). This correlation was influenced by viraemia level and was better at lower viral loads. The proportion of sera with undetectable viral load was 15% with bDNA, 9.7% with MONITOR and 7.7% with SUPERQUANT. For the three measurements, the best cut-offs of sustaine d response to IFN treatment were located at their detection threshold. Amon g patients with viral load below the detection level, a sustained response was observed in 35% tested with bDNA, 38% with MONITOR and 80% with SUPERQU ANT. Hence a stronger correlation was observed between bDNA and SUPERQUANT than between either of these assays and MONITOR. SUPERQUANT was the most se nsitive assay and this greater sensitivity was associated with a better pre dictive value of treatment response.