Acknowledgements We appreciated the contributions of Ana

Acknowledgements We appreciated the contributions of Ana Carolina Galha, Selma XSL Pinheiro and Islene Azevedo for technical assistances. In addition, we wish to thank Adilson José de Almeida (in memoriam), Moyra M Portilho, Vanessa A Marques and Letícia P Scalioni, for data analysis during the set up of this project.
Background and objectives HCV RNA viral load (VL) testing is indicated for patients prior to and during treatment with antivirals, as well as post treatment to evaluate achievement of sustained virologic response (SVR) [1], [2], [3]. Monitoring may also be used in patients with suspected antiviral resistance and as a measure of treatment adherence in groups at risk for poor compliance [1], [4]. There are several assays currently available for the quantification of HCV based on real-time PCR quantification. These methods are recommended based on their excellent analytical sensitivity, specificity, accuracy, and broad dynamic range of linear quantification. Many systems are designed to use separate instruments for extraction and amplification steps. Batching of tests is often required to help keep costs at a moderate level. Both can negatively affect the time to result. Beckman Coulter's DxN VERIS Molecular Diagnostic System (DxN VERIS System) is a new, fully automated system for the quantitative analysis of molecular targets. The system integrates sample introduction, nucleic 17-Hydroxyprogesterone mg extraction, reaction set-up, real-time PCR amplification and detection using TaqMan® chemistry, and results interpretation. The VERIS HCV Assay is a RNA-based quantitative nucleic acid amplification based assay for HCV, calibrated to the 4th WHO International HCV Standard (NIBSC 06/102). The objective of this study was to compare the HCV VLs obtained with the VERIS HCV Assay (VERIS Assay) to those obtained with the Roche COBAS® AmpliPrep/COBAS® TaqMan® HCV Test (COBAS Test) and Abbott RealTime HCV Assay (RealTime Assay) from clinical patient samples at multiple sites in the European Union. Additionally, data from patients being monitored for HCV VL were also compared between VERIS Assay and the two comparators.
Study design
Results
Discussion In these studies, we have compared HCV VL quantification with the VERIS Assay to the COBAS Test and RealTime Assay. Bias between the VERIS Assay and COBAS Test and the VERIS Assay and RealTime Assay showed an overall mean difference of 0.04 log10IU/mL and 0.21 log10IU/mL, respectively. The bias was inconsistent across the range of the assay, varying from −0.42 log10IU/mL at the low end to 0.28 log10IU/mL at the high end for the VERIS Assay versus COBAS Test and 0.0 log10IU/mL at the low end and 0.41 log10IU/mL at the high end for the VERIS Assay versus RealTime Assay. The negative bias at the low end with COBAS Test is likely due to sparse data in the range <4 log10IU/mL, as the regression curve is driven by the large number of samples at the high end. Most of the samples at the low end fall along the identity line rather than the regression line. Data for the RealTime Assay comparison is more equally distributed across the range and therefore the regression curve is less driven by the high end samples. Dilution linearity of the VERIS Assay has been demonstrated previously for all HCV genotypes [6]. A recent comparison of the VERIS Assay and COBAS Test with more equal distribution of samples across the assay range demonstrated better agreement than was seen with our study [7]. Patient monitoring profiles of samples tested with VERIS Assay and COBAS Test and VERIS Assay and RealTime Assay showed similar patterns, indicating, with all other clinical factors being equal, that quantification results are likely to lead to similar clinical decisions based on current practice guidelines [1], [2], [3]. Therapy decisions are based on several factors including treatment naïve versus experienced, HCV genotype (GT), severity of disease, pre-treatment HCV RNA levels and known mutations conferring resistance [1], [2], [3]. Positive bias seen at the 6 log10IU/mL level for the VERIS Assay could affect decisions regarding therapy length for treatment-naïve GT1 HCV patients. For these patients, guidelines indicate a shorter treatment regimen of 8 weeks in lieu of 12 weeks is possible if pre-treatment HCV VL levels are below 6 log10IU/mL. Higher results returned for the VERIS Assay versus both COBAS Test and RealTime Assay, 0.23 log10IU/mL and 0.41 log10IU/mL at 6 log10IU/mL, respectively, could potentially result in more patients receiving a longer treatment regimen. One would expect, however, regardless of assay used, that patients near 6 log10IU/mL would be treated conservatively with the longer regimen, especially considering assay variability.