HIV testing, done repeatedly over time, is a cornerstone of both antenatal care (ANC) and PrEP care. In many settings, HIV rapid tests are done in sequence to confirm infection, but discrepant results (i.e. one positive, one negative) can occur. Guidelines are lacking for how to make treatment decisions after discrepant rapid results in the context of pregnancy and PrEP where urgent antiretroviral treatment (ART) to prevent mother-to-child transmission could be indicated but inappropriate ART may have negative psychosocial, interpersonal, and health systems impacts.
In a cluster randomized trial in Kenyan public health programs (NCT03070600), PrEP is offered to HIV seronegative women at ANC. Repeat HIV testing is done at each follow-up visit (monthly in pregnancy, tri-monthly in postpartum). The Kenyan national HIV testing algorithm indicates that if one rapid (Determine) is reactive, a second (First Response) is performed; if discrepant, both tests are repeated by a separate provider and a DNA PCR is performed using standard of care national referral systems.
Among 2,231 women enrolled during pregnancy and followed for postpartum care, 3,135 repeat HIV tests have been performed, 7 of which had discrepant rapid results (0.22%, 95% CI: 0.09-0.46%) among 5 individuals. DNA PCR samples were collected on the same day as discrepant results; median time to receipt of PCR results was 22 days (range 16-37). In all 5 initial cases, DNA PCR was negative and none of the women were initiated on ART. Two of 5 women subsequently had repeat discrepant rapid results with repeat negative PCRs, one of whom had subsequent concordant positive rapid results (PCR pending) at delivery and declined ART due to disbelief in rapid test results.
False positive results are expected to occur at a low frequency with repeated rapid testing. For individuals who are pregnant or using PrEP, positive results demand urgent ART, but false results could trigger inappropriate ART. As repeat HIV testing during pregnancy and PrEP monitoring expands, the volume of discrepant rapid test results will increase. Our data provide evidence that discrepant results are more likely false positive than true positive. Management of discrepant results needs to balance benefits of rapid ART for PMTCT among true positives, with specific counseling about temporary ART and ‘disclosure’ among women with false positive results. Expedited point-of-care HIV PCR could prevent unclear diagnosis, messaging, and treatment.