Comparative evaluation of the performance of the Abbott RealTime HIV-1
assay for measurement of HIV-1 plasma viral load on genetically diverse
samples from Greece
Background: HIV-1 is characterized by increased genetic heterogeneity
which tends to hinder the reliability of detection and accuracy of HIV-1
RNA quantitation assays.
Methods: In 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.
Results: A 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) log(10) 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 log(10)
copies/ml, respectively. Overall, differences were less than 0.5 log(10)
for 85% of the samples, and >1 log(10) 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) log(10) 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 log(10) copies/ml,
respectively. Overall, the majority of samples (86%) differed by less
than 0.5 log(10), while none of the samples showed a deviation of more
than 1.0 log(10).
Conclusions: In 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