Brief Report: Impact of Early Antiretroviral Therapy on the Performance of HIV Rapid Tests and HIV Incidence Assays.

BACKGROUND

Antiretroviral therapy (ART) can downregulate antibody responses to HIV infection. We evaluated the impact of early vs. delayed ART on the performance of HIV diagnostic and incidence assays.

METHODS

Samples were obtained from 207 participants in the HPTN 052 trial, who were stably suppressed on ART for ≥4 years [Malawi sites; pre-ART CD4 cell count 350-550 cells/mm (early ART arm, N = 180) or <250 cells/mm or an AIDS-defining illness (delayed ART arm, N = 27)]. Samples were tested with 2 HIV rapid tests and 2 HIV incidence assays; selected samples were also tested with two fourth-generation immunoassays and a Western blot (WB) assay. A pre-ART sample was analyzed if the follow-up sample had a false-negative or weakly-reactive rapid test result, or had an incidence assay result indicative of recent infection (false-recent result).

RESULTS

Ten (4.8%) samples had a nonreactive or weakly-reactive rapid test result (7/180 early ART arm, 3/27 delayed ART arm, P = 0.13); one sample had nonreactive fourth-generation assay results and 3 had indeterminate WBs. Forty (18.9%) samples had a false-recent incidence assay result; 16 (7.8%) had false-recent results with both incidence assays. Baseline samples had stronger rapid test and WB bands, higher fourth-generation assay signal-to-cutoff values, and fewer HIV incidence assay results indicative of recent infection.

CONCLUSIONS

False-negative/weakly-reactive HIV rapid tests and false-recent HIV incidence assay results were observed in virally-suppressed individuals, regardless of pre-ART CD4 cell count. Downregulation of the antibody response to HIV infection in the setting of ART may impact population-level surveys of HIV prevalence and incidence.