Heterogeneity of false reactivity profiles of HIV assays while optimizing national HIV testing algorithms: Findings from a multi-country analysis.

This study highlights the importance of verifying HIV testing algorithms to reduce the risk of misdiagnoses caused by common false reactivity. Between 2020 and 2023, WHO supported 14 countries to assess rates of false reactivity and shared false reactivity across HIV rapid diagnostic tests (RDTs) used in HIV testing services. The study involved 26,278 results from 22 different RDT products, with sample sizes ranging from 100 to 302 results per country. The number of RDT products assessed varied between 4 and 13 per country. False reactivity rates ranged from 0 % to 3.32 %, with one country reporting a high false reactivity rate of over 4 % for one RDT. Five countries have no shared false reactivity between RDTs, while the remaining eight countries shared false reactivity across one to six pairs of RDT products. These findings were used to inform national policy, with more than 90 % of countries introducing new RDT products into their HIV testing algorithm based on these results. The study concludes that rates of false reactivity and shared false reactivity between RDT products vary across countries. Therefore, conducting verification studies is crucial for updating national HIV testing algorithms and ensuring accurate diagnosis while also facilitating the market entry of new HIV testing products.