AI Insight
This national evaluation of Malawi's HIV testing program found that implementing the WHO's three-test strategy (requiring three consecutive positive results for diagnosis) instead of the previous two-test approach prevented approximately 997 false-positive diagnoses over three years among nearly 10 million testing encounters. The strategy showed excellent implementation fidelity (99.98% adherence) and positive predictive value, with 82.5% of cases that would have been misdiagnosed under the two-test system ultimately confirmed as HIV-negative. The incremental cost was $471 per false-positive diagnosis prevented, with costs offset within 7.3 years through avoided unnecessary antiretroviral therapy expenses.
Why it matters
False-positive HIV diagnoses carry serious psychological, social, and economic consequences for individuals while wasting healthcare resources on unnecessary treatment. This large-scale real-world evidence demonstrates that the WHO three-test strategy can effectively reduce diagnostic errors in settings where HIV prevalence is declining, providing a roadmap for other countries considering similar policy changes.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Background: In 2019, WHO recommended three consecutive reactive serological test results for HIV diagnosis to reduce false-positive diagnoses. Malawi changed from a two-test to a three-test strategy in 2022 as HIV test positivity declined. We assessed diagnostic performance, implementation fidelity, and costs. Methods: We analysed national HIV testing data from Nov 1, 2022, to Oct 31, 2025. Using observed three-test classifications as the reference standard, we reconstructed classifications under the two-test strategy. We estimated positive predictive value (PPV), implementation fidelity, potential false-positive diagnoses prevented, incremental costs, and time to offset testing costs through avoided antiretroviral therapy expenditure. Results: Among 9,885,599 encounters eligible for implementation-fidelity analysis, 99.98% followed a valid three-test pathway. The diagnostic-performance analysis included 9,862,908 encounters, of which 171,351 (1.7%) were classified HIV-positive and 9,138 (0.09%) were inconclusive. Under the two-test strategy, 1,209 inconclusive encounters with a T1+/T2+/T3- sequence would have been classified as HIV-positive. Retesting and reference-laboratory data indicated that 82.5% of these would subsequently be classified as HIV-negative, corresponding to 997 false-positive diagnoses prevented (10.3 per 100 000 three-test non-positive encounters; 95% CI 9.7-10.9). Retesting within 1-2 weeks was associated with the highest odds of potential false-positive classification (adjusted OR 39.37, 95% CrI 30.63-50.61). The incremental cost was US$471 per false-positive diagnosis averted and was offset within 7.30 years. Conclusions: Malawi’s transition to a three-test HIV testing strategy prevented false-positive diagnoses and unnecessary antiretroviral therapy at modest cost, supporting broader adoption of WHO guidance in similar settings. Funding: Gates Foundation.