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

Abstract

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 European Centres using QUANTIPLEXtrade mark bDNA, MONITOR AMPLICORtrade mark and SUPERQUANTtrade mark assays. Analyses were performed on the same sample. Viral genotype was assessed using INNO-LiPA HCV II kits. Intercentre variations were observed 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 bDNA and MONITOR (0.677) and between MONITOR and SUPERQUANT (0.632). These discrepancies were greatest with genotype 2 (bDNA/SUPERQUANT= 0.772; bDNA/MONITOR=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 sustained response to IFN treatment were located at their detection threshold. Among patients with viral load below the detection level, a sustained response was observed in 35% tested with bDNA, 38% with MONITOR and 80% with SUPERQUANT. Hence a stronger correlation was observed between bDNA and SUPERQUANT than between either of these assays and MONITOR. SUPERQUANT was the most sensitive assay and this greater sensitivity was associated with a better predictive value of treatment response.

Use and interpretation of virological tests for hepatitis C

“…The specificity of the assays is of the order of 98% to 99%, and quantification is independent of the HCV genotype. [37][38][39][40][41][42][43] Whatever the assay, differences or variations of less than 0.5 log (i.e., less than 3-fold) should not be taken into account, as they may be due to intrinsic or between-patient variability. 44 No tests for HCV RNA quantification have yet been approved in the United States, but several are likely to be approved in the future.…”

Prediction of treatment outcome in patients with chronic hepatitis C: Significance of baseline parameters and viral dynamics during therapy

“…3,4,10 General application may be difficult due to the previous lack of standardization of HCV-RNA detection methods. [11][12][13][14] The HCV-RNA detection assay applied in several pivotal trials (Superquant; NGI, Los Angeles, CA) is not generally available outside the United States. Furthermore, current algorithms for treatment of chronic hepatitis C may have been influenced by marketing interests of pharmaceutical companies who designed and analyzed these multicenter trials.…”

Treatment of chronic hepatitis C: Improved combination therapy

“…Finally, it must be recognized that utilization of stopping rules based on quantitative testing has some potential pitfalls. HCV RNA levels are dependent on sample processing and assay methodology [45][46][47][48]. Although there are now at least [43]; with permission.)…”

“…Although there are now at least [43]; with permission.) three commercially available quantitative assays for HCV RNA that correlate reasonably well in samples with low levels of HCV RNA, results with one assay cannot be compared with another because the dynamic ranges of the tests differ significantly [46,47]. Furthermore, the recent attempt to standardize assays using World Health Organization units for viral quantitation has further confused interpretation of tests because the published conversion factors disagree with those of the manufacturers [48].…”