Assessing diagnostic accuracy of Ov16 rapid diagnostic tests for onchocerciasis using Bayesian latent class models

BackgroundOnchocerciasis elimination programs increasingly rely on tests that detect antibodies to the Ov16 antigen, yet the performance of currently available rapid tests remains uncertain. The existing Ov16 rapid test shows inconsistent sensitivity when used on whole blood and does not consistently meet international thresholds for mapping or stopping mass drug administration. Two new Ov16 rapid tests have recently been developed, but their accuracy has not been fully evaluated using methods that account for the lack of a true reference standard. Methodology/Principal FindingsWe pooled data from three field studies conducted in Mozambique, Ghana, and Benin in 2023 to evaluate two novel Ov16 rapid tests alongside the existing test. A Bayesian latent class model was used to estimate sensitivity and specificity without assuming that any test was perfect. Across all model specifications, the GADx rapid test showed the highest sensitivity, consistently exceeding the 89% threshold recommended for decisions to stop mass drug administration (posterior medians: 92.0%-92.8%). The SD Bioline test met this threshold in most models but showed lower sensitivity in one model (83.2%). The DDTD test demonstrated lower sensitivity overall (86.6%-88.4%). Specificity estimates were uniformly high for all tests but remained below the recommended threshold of 99.8% (highest median: 98.8%). Alternative definitions of a positive result for the multi-antigen DDTD test did not materially change its performance. Conclusions/SignificanceThe two novel rapid tests showed improved sensitivity relative to the existing test, particularly the GADx test. However, none of the tests achieved the specificity level needed to support decisions to stop mass drug administration on their own. These findings highlight the need for improved diagnostic tools or confirmatory testing strategies as countries work toward onchocerciasis elimination. Author SummaryIn this study, we evaluated three rapid tests used to detect exposure to the parasite that causes river blindness. These tests are important tools for country programs that are trying to eliminate the disease and decide when to stop giving communities preventive treatment. One challenge is that there is no perfect test to compare new tools against. To address this, we combined data from studies in Mozambique, Ghana, and Benin and used a statistical approach that estimates test accuracy without relying on a single reference test. We found that one of the new tests, made by GADx, identified people with exposure more accurately than the others. The existing test and the DDTD test showed lower accuracy. All three tests correctly identified most people who were not exposed, but not at the very high level needed for programs to confidently stop treatment. Our results show that while new rapid tests are improving, more work is needed to create tools that are accurate enough for elimination decisions. This information can help guide public health programs as they work toward ending river blindness.