A multi-center study comparing the analytical sensitivity and clinical concordance of three HIV-1 viral load assays.

BACKGROUND: HIV-1 viral load assays are essential tools for clinical management of people living with HIV-1. OBJECTIVES AND STUDY DESIGN: We evaluated concordance between three assays: the cobas® HIV-1 test for use on the cobas® 6800 and cobas® 8800 systems (cobas HIV-1); the COBAS® TaqMan® HIV-1 Test, v2.0 for use with the High Pure System and the COBAS® AmpliPrep/COBAS® TaqMan® HIV-1 test, v2.0. Analytical sensitivity, precision and accuracy of all three methods were assessed using the WHO 2nd International Standard for HIV-1, with concentrations from 5 to 1000 copies/mL. Accuracy and concordance were evaluated using 212 clinical specimens. Overall percent agreement (OPA) was determined using three different thresholds used as medical decision points. RESULTS: The limit of detection was below 20 copies/mL for each assay. The hit rate for each assay was 100 % for concentrations ≥ 50 copies/mL. Only the cobas HIV-1 test generated quantifiable data for all replicates at 50 copies/mL. Between 50 and 400 copies/mL, results for all assays were accurate within 0.09 log10 copies/mL, with standard deviation less than 0.14 log10 copies/mL. The mean difference between paired results in clinical specimens ranged from -0.050 to 0.107 log10 copies/mL across all assay comparisons. The OPA between pairs of assays ranged from 94.8 to 98.1% at the 50 copies/mL cutoff, and improved to a range of 97.6-99.0% at the 200 copies/mL cutoff. At the 1000 copies/mL cutoff, OPA between assays was 98.5-99.0%. CONCLUSIONS: The cobas HIV-1 assay is highly sensitive, accurate and suitable for use in clinical practice.

Commutability and concordance of four hepatitis B virus DNA assays in an international multicenter study.

BACKGROUND: HBV DNA is the most important molecular marker in hepatitis B, used to determine treatment indication and monitoring. Most patients require lifelong hepatitis B virus (HBV) management, thus viral load (VL) monitoring may be performed at different laboratories, with different HBV assays, which may result in different VL results. This multicenter study compares the commutability and concordance of results from four different HBV DNA assays: CAP/CTM HBVv2, HPS/CTM HBVv2 and the new cobas 6800/8800 HBV and cobas 4800 HBV assays. METHODS: Across all four assays, HBV limit of detection (LoD) and linearity at lower concentrations were assessed using panels traceable to the World Health Organization international standard, and concordance was investigated at the important medical decision cutoffs 2000 and 20,000 IU/ml, using specimens from HBV-positive patients. RESULTS: The calculated LoD via a probit curve was 2.7 IU/ml for cobas 6800/8800 HBV, 2.8 IU/ml for cobas 4800 HBV, 9.6 IU/ml for CAP/CTM HBVv2, and 6.2 IU/ml for HPS/CTM HBVv2. The average accuracy was comparable between cobas 6800/8800 HBV, cobas 4800 HBV and CAP/CTM HBVv2 (0.04-0.05 log10 IU/ml), while a slightly lower accuracy was documented for HPS/CTM HBVv2 (-0.16 log10 IU/ml). A total of 211-245 clinical samples were used for a pairwise comparison. Mean paired log differences ranged from -0.17 log10 IU/ml to -0.01 log10 IU/ml. Coefficient of determination was over 98% for all pairs with high overall percent agreement at the 2000 and 20,000 IU/ml cutoffs (from 91.7% to 96.3%). In a subset of samples with VL±0.5 log10 to the 2000 and 20,000 IU/ml thresholds, concordance was still 72% and 82%, respectively. CONCLUSIONS: The new cobas 6800/8800 HBV and 4800 HBV assays show high accuracy in samples with low-level viremia and a high concordance with the established HBV tests, CAP/CTM HBVv2 and HPS/CTM HBVv2, at 2000 and 20,000 IU/ml. Thus, all four HBV assays have high commutability and may be used interchangeably in routine clinical practice.

Multicenter Comparison Study of both Analytical and Clinical Performance across Four Roche Hepatitis C Virus RNA Assays Utilizing Different Platforms.

The efficacy of antiviral treatment for chronic hepatitis C virus (HCV) infection is determined by measuring HCV RNA at specific time points throughout therapy using highly sensitive and accurate HCV RNA assays. This study compared the performances of two recently developed real-time PCR HCV RNA assays, cobas HCV for use on the cobas 6800/8800 systems (cobas 6800/8800 HCV) and cobas HCV for use on the cobas 4800 system (cobas 4800 HCV), with those of two established assays, the Cobas AmpliPrep/Cobas TaqMan HCV quantitative test, version 2 (CAP/CTM v2) and the Cobas TaqMan HCV test, version 2 for use with the High Pure system (HPS/CTM v2). The limits of detection (LODs) and linearity at lower concentrations (5 to 1000 IU/ml) were assessed for cobas 6800/8800 HCV and cobas 4800 HCV using WHO standard traceable panels representing HCV genotypes (GT) 1 to 4. Pairwise assay comparisons were also performed using 245 clinical samples representing HCV GT 1 to GT 4. Results from cobas 6800/8800 HCV and cobas 4800 HCV were linear at low HCV RNA concentrations (<0.3 log10 IU/ml difference between expected and observed results) with LODs of 8.2 IU/ml and 11.7 IU/ml, respectively, for GT 1. The new assays showed excellent agreement with results from CAP/CTM v2 and HPS/CTM v2 in samples with quantifiable viral loads. The concordances using the 6 million IU/ml cutoff were high among all four assays (90 to 94%). In conclusion, the cobas 6800/8800 HCV and cobas 4800 HCV tests are sensitive and linear and correlate well with the established Roche assays used in clinical practice.

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.