Ability of Two Commercially Available Assays (Abbott RealTi m e HIV-1 and Roche Cobas AmpliPrep/Cobas TaqMan HIV-1 Version 2.0) To Quantify Low HIV-1 RNA Levels (<1,000 Copies/Milliliter): Comparison with Clinical Samples and NIBSC Working Reagent for Nucleic Acid Testing Assays

Abstract

Concordance between molecular assays may be suboptimal at low HIV-1 viremia levels (<1,000 copies/ml); therefore, it may be difficult to define and compare virologic endpoints for successful and failed therapy. We compared two commercial assays (the Abbott RealTime HIV-1 and the Roche Cobas AmpliPrep/TaqMan HIV-1 version 2.0) for their ability to detect and quantify low viral loads. A comparison was performed using 167 residual clinical samples (with values ranging from "not detected" to 1,000 copies/ml, as measured by the Abbott assay) and the National Institute and Biological Standards and Control (NIBSC) HIV-1 RNA working reagent 1 for nucleic acid amplification techniques (NAT) assays (serially diluted to a range from 1 to 1,000 copies/ ml). Quantitative results were compared using Lin's concordance correlation coefficient and a Bland-Altman plot. Concordance with the qualitative results was measured by Cohen's kappa statistic. With clinical samples, the degree of interassay concordance of the qualitative results at a 40-copies/ml HIV-1 RNA threshold was substantial ( ‫؍‬ 0.762); the correlation among the quantified samples was suboptimal (concordance correlation coefficient, 0.728; P < 0.0001); the mean difference of the values between the Roche and Abbott assays was 0.193 log 10 copies/ml. Using the HIV-1 RNA working reagent 1 for NAT assays, the results provided by the Roche assay were, on average, 3 times higher than expected, while the Abbott assay showed high accuracy. The Roche assay was highly sensitive, being able to detect a level as low as 3.5 copies/ml HIV-1 RNA with 95% probability. The performance characteristics of each molecular assay should be taken into account when HIV-1 RNA threshold values for "virologic suppression," "virologic failure," "persistent low viral loads," etc., are defined and indicated in the support of clinical decisions.

Factors associated with virological rebound in HIV-infected patients receiving protease inhibitor monotherapy

“…This result is consistent with several studies that tested samples in parallel with these two assays and found that Taqman-2 has greater sensitivity for detecting low-level HIV RNA [22,23].…”

Evaluation of Performance Characteristics of the Aptima HIV-1 Quant Dx Assay for Detection and Quantitation of Human Immunodeficiency Virus Type 1 in Plasma and Cervicovaginal Lavage Samples

“…There are two FDA-approved HIV-1 real-time assays that are used by most clinical laboratories, the Cobas AmpliPrep/Cobas TaqMan HIV-1 test (Roche Molecular Systems Inc., Pleasanton, CA) and the RealTime HIV-1 assay (Abbott Molecular). Studies have compared the performance characteristics of these assays (17)(18)(19); more recent reports (20)(21)(22) have assessed the performance characteristics of the Aptima assay and shown excellent overall performance in detection and accurate quantification of all the major HIV-1 subtypes, and viral load values agreed well with those of other established assays. Our results confirmed these findings; the Aptima assay had good linearity over the quantification range of the assay tested, and plasma viral load results were highly correlated with the RealTime results (R 2 ϭ 0.99), with a comparable coefficient of variance of Ͻ5.5%.…”

Evaluation of the RealTime HIV-1, Xpert HIV-1, and Aptima HIV-1 Quant Dx Assays in Comparison to the NucliSens EasyQ HIV-1 v2.0 Assay for Quantification of HIV-1 Viral Load

“…The NucliSens v2.0 assay has been shown to be less precise than the Roche Cobas AmpliPrep/Cobas TaqMan v2.0 (15) and Versant bDNA (8) assays. The RealTime assay was reported to have excellent intra-assay and interassay reproducibility (10% variability) at low viral loads (12) and to be more accurate than Roche assays (16,17), although greater variability (30%) at a high viral load (6 log copies/ml) (12) and a tendency to underquantify lowviremic samples have been reported (18)(19)(20). In a recent large international collaborative study using 4,221 paired samples, the overall correlation and concordance between several viral load assays (including the RealTime assay) were found to be lower at low viral loads than at higher loads (21 and high correlation values, with overall minimal mean viral load differences between the two assays (0.04 log copies/ml) (8,22).…”