Evaluation of the Aptima HIV-1 Quant Dx assay for HIV diagnosis at birth in South Africa

Abstract

The increased coverage of antiretroviral therapy has resulted in a decrease in the positive predictive value (PPV) and diagnostic sensitivity of early infant diagnosis assays. To evaluate the diagnostic performance of the Aptima HIV-1 Quant DX assay (Aptima) in detecting HIV infection at birth. The study was a cross-sectional laboratory based evaluation using whole blood DBS specimens. Samples were collected from HIV-exposed neonates at birth at two paediatric facilities in Gauteng between 1st March 2018 - 31st January 2020. Performance of the Aptima compared to the Cobas® AmpliPrep/Cobas® TaqMan HIV-1 Qualitative Test v2.0 was calculated using a two-by-two table and reported as proportions with 95% confidence intervals. A total of 363 infants met the inclusion criteria of which 4 (1.1%) had an Aptima result discordant with CAP/CTM HIV status: two (50%) negative and two (50%) positive. The Aptima assay had a sensitivity of 93.75% (95% CI: 79.19%-99.23%), specificity of 99.4% (95% CI: 97.83%-99.93%), PPV of 93.75% (95% CI: 78.98%-98.36%), negative predictive value of 99.4% (95% CI: 97.73%-99.84%), and overall accuracy of 98.9% (95% CI: 97.2%-99.7%). The Aptima yielded an error code on 37 (10.19%) results, of which 35 (94.59%) were resolved on repeat testing. Of the 32 HIV-detected specimens, 20 had a plasma VL result available (18 on Abbott and 2 on Cobas). The absolute median difference was 0.66 log10 (IQR: 0.36-1.71). The Aptima demonstrated good EID performance and can be considered as a qualitative EID assay.