Routine monitoring of HIV-1 RNA, or viral load (VL) in patients on antiretroviral therapy (ART) is important, but there are multiple impediments to VL testing in resource-constrained settings. An accurate point-of-care (POC) HIV-1 VL test could alleviate many of these challenges.
We compared the performance of the Cepheid Xpert® HIV-1 VL against the laboratory-based Abbott m2000sp/m2000rt assay (Abbot assay). ART-naïve individuals participating in the Botswana Combination Prevention Project in 20 communities provided EDTA blood specimens during household surveys.
Both POC Xpert HIV-1 VL and Abbott assays were performed on specimens sampled from 277 individuals. We found high correlation between the Xpert HIV-1 VL and Abbott assay results (r(2) = 0.92; p<0.001). The overall mean difference in the HIV-1 RNA values obtained by Xpert HIV-1 VL assay and Abbott assay was 0.34 (95%CI: 0.26-0.40) log10 copies/mL (p<0.001). Using a clinically relevant level of 1,000 copies/mL as a threshold, agreement was 90.6% (95%CI 87.9-93.1%) with sensitivity of 98.6% (95%CI 97.2-100%). Both methods agreed on detectability of HIV-1 RNA (>40 copies/mL) in 97.1% (95%CI 95.5-98.7%) with sensitivity of 99.6% (95%CI 97.2-100%).
The POC Cepheid Xpert HIV-1 VL assay showed high agreement and accuracy with a laboratory-based method of HIV-1 RNA testing. The POC Xpert HIV-1 VL assay tended to overestimate HIV-1 VL, although the difference was below a clinically relevant threshold of 0.5 log10 copies/mL. The POC Cepheid Xpert HIV-1 VL assay is a promising tool for monitoring patients on ART in Southern Africa.