Verification of False Reactivity in HIV Rapid Diagnostic Tests and Its Translation Into the Three Tests Algorithm in Cameroon

BACKGROUND: In a context of HIV seropositivity below 5%, transitioning from a two- to a three-test algorithm is required to secure positive predictive values > 99% for mitigating false reactivity. With Cameroon having 2.7% seroprevalence, we sought to ascertain events of false reactivity from eight WHO-prequalified HIV rapid diagnostic tests (RDTs) and design suitable combinations for the country three-test algorithm. METHODS: A facility-based study was conducted in July-August 2021 among 172 consenting clients attending health facilities in Yaoundé-Cameroon. Whole blood was collected and samples characterized in parallel using KHB Diagnostic Kit for HIV (1 + 2) Antibody and INNO-LIA HIV I/II Ag/Ab to rule out reactive cases. Two lots of each selected RDT were tested simultaneously in quadruplicate on HIV non-reactive samples and repeated by a different tester. RDTs were considered false positive if any reactivity was detected. RESULTS: Following characterization, 25 samples were HIV-reactive (i.e., ruled out) and 147 non-reactive. Following random selection, 100 non-reactive samples tested for false reactivity revealed: 0% (0/100) First Response HIV 1-2-O Card, 0% (0/100) First Response HIV1 + 2/Syphilis Combo, 0% (0/100) STANDARD Q HIV/Syphilis Combo, 0% (0/99) ONE STEP Anti-HIV1&2 (one invalid result); 1% (1/100) Determine HIV Early Detect and Bioline HIV/Syphilis Duo, 2% (2/100) Alere Determine HIV-1/2, 4% (4/100) Rapid Test for Antibody to HIV. CONCLUSION: In the Cameroonian context, HIV false reactivity ranged from 0% to 4% across selected RDTs. Thus, a reliable three-test algorithm ranks First Response HIV 1-2-0 Card, First Response HIV1 + 2/Syphilis Combo or STANDARD Q as suitable RDT-1 to mitigate false-positive events at the country-level.