Evaluation of the COBAS(®) AmpliPrep/COBAS(®) TaqMan(®) HCV Test, v2.0 and comparison to assays used in routine clinical practice in an international multicenter clinical trial: The ExPECT study.

BACKGROUND: The COBAS(®) AmpliPrep(®)/COBAS(®) TaqMan(®) HCV Test, v2.0 (CAP/CTM2) is used for HCV RNA viral load monitoring. OBJECTIVES: The performance of the CAP/CTM2 was compared to other widely used tests, including a manual version of the assay (the COBAS(®) TaqMan(®) HCV Test, v2.0 for use with the High Pure System, HPS/CTM2) predominantly used during phase III clinical trials for the new direct acting antiviral therapies. STUDY DESIGN: Low HCV RNA level comparisons were performed across tests (Abbott Realtime HCV Test, ART; COBAS(®) AmpliPrep(®)/COBAS(®) TaqMan(®) HCV Test, v1.0, CAP/CTM1; CAP/CTM2; and HPS/CTM2) using dilutions of the 2nd HCV WHO International Standard. Additionally, the clinical performance of the CAP/CTM2 was evaluated with 421 leftover HCV RNA-positive routine clinical samples. RESULTS: All quantifiable WHO dilutions were within ±0.3log10IU/mL of the expected results across tests and the analytical sensitivity resulted in a limit of detection of 12IU/mL (95% confidence interval, 10, 15). When clinical samples were tested the results for 87% (367 of 421) of all sample comparisons were within ±0.5log10IU/mL. When low viral load results (25-3500IU/mL) were compared, values obtained by the ART assay were significantly lower (p<0.0001) than those obtained with the CAP/CTM2. CONCLUSIONS: The new CAP/CTM2 showed good accuracy with comparable sensitivity to comparator assays. The new kit is well-suited for use in the routine diagnostic laboratory, especially for accurate monitoring of patients receiving triple therapy or interferone-free regimens.

Analytical and clinical performance of a new molecular assay for Epstein-Barr virus DNA quantitation.

Quantitation of EBV DNA has been shown to be a useful tool to identify and monitor patients with immunosuppression and high risk for EBV-associated disease. In this study, the analytical and clinical performance of the new Realquality RS-EBV Kit (AB Analitica, Padova, Italy) was investigated. The clinical performance was compared to that of the EBV R-gene (bioMerieux, Varilhes, France) assay. When the accuracy of the new assay was tested, all results except of one were found to be within ±0.5log10 unit of the expected panel results. Determination of linearity showed a quasilinear curve, the between day imprecision ranged from 18% to 88% and the within run imprecision from 16% to 53%. When 96 clinical EDTA whole blood samples were tested, 77 concordant and 19 discordant results were obtained. When the results for the 69 samples quantifiable with both assays were compared, the new assay revealed a mean 0.31log10 unit higher measurement. The new assay proved to be suitable for the detection and quantitation of EBV DNA in EDTA whole blood in the routine diagnostic laboratory. The variation between quantitative results obtained by the assays used in this study reinforces the use of calibrators traceable to the existing international WHO standard making different assays better comparable.

Genotype impact on HCV RNA levels determined with the VERSANT HCV RNA 1.0 assay (kPCR).

BACKGROUND: Accurate quantitation of hepatitis C virus (HCV) RNA is mandatory for the management of anti-HCV therapy. OBJECTIVES: The genotype-dependent performance of the new commercially available VERSANT HCV RNA 1.0 Assay (kPCR) and the COBAS AmpliPrep/COBAS TaqMan HCV Quantitative Test, version 2.0 was investigated. STUDY DESIGN: The molecular assays for quantitation of HCV RNA were performed according to the manufacturer's package insert instructions. HCV genotypes/subtypes/isolates, and mutations in the 5'NCR were detected by direct sequencing. RESULTS: When members of a worldwide HCV performance panel including HCV subtypes 1a, 1b, 2a, 3b, and 4a were tested with the Siemens assay and the results were compared with those obtained by the Roche assay, the mean log10 unit differences for members containing HCV subtypes 1a, 1b, 3b, and 4a were found to be within ±0.5 log(10) units. For the panel member containing HCV subtype 2a, the HCV RNA concentration was found to be >0.5 log(10) units lower with the Siemens assay. When clinical samples were tested, the HCV RNA concentration of all samples containing HCV subtype 2a were found to be >0.5 log(10) units lower with the Siemens assay while that of certain HCV subtype 3a and 4a isolates were found to be >1.0 log(10) units lower. CONCLUSION: The VERSANT HCV RNA 1.0 Assay substantially underestimates HCV RNA concentrations in HCV subtype 2a samples and in HCV subtype 3a and 4a samples containing certain isolates. This may be caused by mismatches with the target sequences due to the primer and/or probe design.