Comparative evaluation of the Artus HIV-1 QS-RGQ assay and the Abbott RealTime HIV-1 assay for the quantification of HIV-1 RNA in plasma

Background: The quantitative measurement of HIV-1 RNA levels in plasma ('viral load') is essential in the management of HIV-infected patients. Objective: The new Artus HIV-1 QS-RGQ assay ('ArtusHIV') for HIV-1 RNA quantification in plasma was compared to the Abbott RealTime HIV-1 assay ('RealTime') following automated RNA isolation by the QIAsymphony and Abbott m2000 extractors, respectively. Emphasis was placed on assay performance with diverse HIV-1 subtypes and in patients receiving antiretroviral therapy (ART). Study design: Plasma from 211 patients (105 subtype B, 87 non-B subtypes; 147 on ART) and serial dilutions of the WHO 2nd International HIV-1 RNA Standard (WHO-IS) were tested by the two assays in parallel. Assay relationship and agreement were determined by linear regression, correlation analysis, and Bland-Altman analysis. Results: With 125 specimens quantified by both assays, measurements were linearly associated and strongly correlated. Overall Artus reported higher levels by mean 0.24 (95% confidence interval [CI] 0.16-0.32) log10 copies/ml (P<0.0001); 5 samples (subtypes A, B, CRF01, CRF03) fell outside the 95% agreement. Discordant results were obtained with 11 and 13 samples quantified by either ArtusHIV or RealTime alone respectively, at levels generally close to the lower limit of quantification, giving an overall discordance rate of 24/211 (11%). Both assays generally under-quantified the WHO-IS by between 0.1 and 0.4 log10 copies/ml across seven dilutions. Conclusions: The ArtusHIV assay offers performance comparable to that of the RealTime assay across a wide range of HIV-1 subtypes and among both treated and untreated patients