Abstract
BackgroundHIV-1 is characterized by increased genetic heterogeneity which tends to hinder the reliability of detection and accuracy of HIV-1 RNA quantitation assays.MethodsIn this study, the Abbott RealTime HIV-1 (Abbott RealTime) assay was compared to the Roche Cobas TaqMan HIV-1 (Cobas TaqMan) and the Siemens Versant HIV-1 RNA 3.0 (bDNA 3.0) assays, using clinical samples of various viral load levels and subtypes from Greece, where the recent epidemiology of HIV-1 infection has been characterized by increasing genetic diversity and a marked increase in subtype A genetic strains among newly diagnosed infections.ResultsA high correlation was observed between the quantitative results obtained by the Abbott RealTime and the Cobas TaqMan assays. Viral load values quantified by the Abbott RealTime were on average lower than those obtained by the Cobas TaqMan, with a mean (SD) difference of -0.206 (0.298) log10 copies/ml. The mean differences according to HIV-1 subtypes between the two techniques for samples of subtype A, B, and non-A/non-B were 0.089, -0.262, and -0.298 log10 copies/ml, respectively. Overall, differences were less than 0.5 log10 for 85% of the samples, and >1 log10 in only one subtype B sample. Similarly, Abbott RealTime and bDNA 3.0 assays yielded a very good correlation of quantitative results, whereas viral load values assessed by the Abbott RealTime were on average higher (mean (SD) difference: 0.160 (0.287) log10 copies/ml). The mean differences according to HIV-1 subtypes between the two techniques for subtype A, B and non-A/non-B samples were 0.438, 0.105 and 0.191 log10 copies/ml, respectively. Overall, the majority of samples (86%) differed by less than 0.5 log10, while none of the samples showed a deviation of more than 1.0 log10.ConclusionsIn an area of changing HIV-1 subtype pattern, the Abbott RealTime assay showed a high correlation and good agreement of results when compared both to the Cobas TaqMan and bDNA 3.0 assays, for all HIV-1 subtypes tested. All three assays could determine viral load from samples of different HIV-1 subtypes adequately. However, assay variation should be taken into account when viral load monitoring of the same individual is assessed by different systems.
Highlights
HIV-1 is characterized by increased genetic heterogeneity which tends to hinder the reliability of detection and accuracy of HIV-1 RNA quantitation assays
Of the 149 samples 127 (85.2%) had a detectable viral load by both assays, 17 (11.4%) were undetectable by both assays and five (3.4%) samples were quantified only by Cobas TaqMan at 43.4, 50.8, 65.5, 257 and 843 copies/ml, respectively whereas the same five samples were reported as having HIV-1 RNA < 40 copies/ml by the Abbott RealTime
Retesting of the discrepant samples by both assays revealed that only one sample characterized as subtype B was repeatedly reactive by Cobas TaqMan (674 copies/ml at retesting), while it was repeatedly non-reactive by Abbott RealTime
Summary
HIV-1 is characterized by increased genetic heterogeneity which tends to hinder the reliability of detection and accuracy of HIV-1 RNA quantitation assays. Quantitative measurement of plasma viral load provides a great insight into the pathogenesis of HIV-1 infection and constitutes an essential parameter of infection prognosis and optimal management of clinical patients [1,2,3,4]. Given the significance of accurate viral load measurements for optimal management of patients, the requirement for ultra-sensitive assays is crucial. A major innovation of target amplification techniques is the development of assays that monitor accumulation of products in real-time, which are characterized by increased sensitivity, expanded dynamic range, diminished risk of contamination and high throughput [13,14]. In Greece increasing genetic diversity of HIV-1 has been documented and an increase over time of the prevalence of non-B subtypes, subtype A infections, has been reported [17]
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