HIV-1 load comparison using four commercial real-time assays

Abstract

The HIV-1 RNA viral load is commonly used for the monitoring of disease progression and antiretroviral treatment of HIV-1-infected patients. Since the misestimating of values could lead to inappropriate therapeutical management, the comparative performances, especially the ability to span the genetic diversity of HIV-1, of available automated real-time assays need to be evaluated. We conducted a prospective study with 74 consenting patients enrolled between March 2007 and November 2008. A blood sample was obtained at the time of diagnosis of HIV seropositivity and blindly tested for HIV-1 RNA by at least 4 commercial tests: the Abbott m2000 RealTime HIV-1, bioMérieux NucliSens EasyQ HIV-1, version 1.2 (v1.2), and Cobas AmpliPrep/Cobas TaqMan (CAP/CTM) v1.0 and v2.0 assays. The means of difference were null between CAP/CTM v2.0 and Abbott for CRF02_AG subtypes but positive in favor of CAP/CTM v2.0 for genotype B and negative in favor of NucliSens for all genotypes. The standard deviation (SD) of difference ranged from 0.3 to 0.59, depending on the considered couples of assays. Reliabilities of these four tests, appreciated by the standard deviation of difference between the measurement and the estimated "true" viral load and by the coefficient of reliability, were significantly different (P < 10(-4)) among each other. Significant differences were also observed within each group of HIV-1 genotype. The global disparity was higher for CRF02_AG than for B subtypes. This study indicates a risk of viral load misestimating or discrepancies between techniques, depending on the HIV-1 subtype, and speaks in favor of using the same assay for the monitoring of HIV-1-infected patients.

FIG. 1.

Bland-Altman analyses of the agreement between couples of HIV viral load assays (in log copies/ml): Abbott m2000 RealTime and NucliSens HIV-1 EasyQ v1.2 (row 1), CAP/CTM v1.0 and NucliSens EasyQ (row 2), CAP/CTM v1.0 and Abbott m2000 RealTime (row 3), CAP/CTM v2.0 and Abbott m2000 RealTime (row 4), CAP/CTM v2.0 and NucliSens EasyQ (row 5), and CAP/CTM v2.0 and CAP/CTM v1.0 (row 6). Bland-Altman analyses were carried out on all the patients (A), on HIV-1 B subtypes (B), and on HIV-1 CRF02_AG subtype (C). The x axis bears the average value for each sample obtained by the two techniques. The y axis bears the difference between the values obtained with the two techniques. The solid lines represent the mean of the differences between the values, and the dashed lines represent the mean of the differences ± 1.96 standard deviation (SD) (95% limits of agreement).