Evaluation of the performance of three biomarker assays for recent HIV infection using a well-characterized HIV-1 subtype C incidence cohort.

BACKGROUND: Biomarkers for detecting early HIV infection and estimating HIV incidence should minimise False-Recent Rates (FRRs) while maximising Mean Duration of Recent Infection (MDRIs). We compared BED capture enzyme immunoassay (BED), Sedia Limiting Antigen Avidity EIA (LAg) and Bio-Rad avidity incident incidence (BRAI) assays using samples from Zimbabwean postpartum women infected with clade C HIV.

METHODS: We calculated MDRIs using 590 samples from 351 seroconverting postpartum women, and FRRs using samples from 2,825 women known to be HIV-positive for >12 months.

RESULTS: Antibody kinetics were more predictable with LAg and had higher precision compared to BED or BRAI. BRAI also exhibited more variability, and avidity reversal in some cases. For BED, LAg and BRAI, used alone or with viral load (VL), MDRI values in days were: BED - 188 and 170 at normalized optical density (ODn) 0.8; LAg - 104 and 100 at ODn cut-off 1.5; BRAI - 135 and 134 at Avidity Index cut-off 30%. Corresponding FRRs were: BRAI 1.1% and 1.0% and LAg 0.57% and 0.35%: these were 3.8 - 10.9 times lower than BED values of 4.8% and 3.8 Conclusion: BRAI and LAg have significantly lower FRRs and MDRIs than in published studies, and much lower than BED and could be used to estimate incidence in perinatal women and to measure population level HIV incidence in HIV control operations in Africa. BRAI and LAg have significantly lower FRRs and MDRIs than in published studies, and much lower than BED. These improved methods could be used to estimate incidence in perinatal women and to measure population level HIV incidence in HIV control operations in Africa.