Concordance between Ov16 rapid diagnostic test(RDT) and Ov16 enzyme-linked immunosorbent assay (ELISA) for the diagnosis of onchocerciasis in areas of contrasting endemicity in cameroon

The diagnosis of onchocerciasis in endemic areas has been demanding given the need to replace the invasive skin snip method with a more sensitive and specific rapid point-of-contact tool. Filarial antigen detection tests are better alternative methods in diagnosing Onchocercal infections, as they detect infections and could be used to monitor transmission in endemic areas following mass drug administration. With the shift in paradigme from control to elimination, a rapid point- of-contact tool is required to support elimination programs. This was a cross-sectional, community-based study conducted in 50 villages selected from six health districts using a systematic sampling technique. Individuals ≥17 years who had lived in the community for a duration of 5 years and above provided blood specimens for IgG4 antibodies testing against O. volvulus antigens. Data were analyzed using SPSS v.20 and expectation maximization to classify optical densities for positive and negative samples from ELISA results. The kappa statistics was used to measure the level of agreement between the two tests. In a total of 5001 participants which were recruited for the study, 4416 (88.3%) participant samples passed the plate quality control criteria and were considered for the test comparison analysis. Out of the 4416 participants, 292 (6.6%) tested positive with Ov16 RDT and 310 (7.0%) with Ov16 ELISA. All those who tested positive with the rapid test agreed positive with ELISA. The overall percentage agreement was 99.2%, the Kappa score of 0.936. The results obtained indicate an excellent agreement between ELISA and RDT as measured by kappa (0.936) which was statistically significant (P < 0.001). Our experience with the Ov16 ELISA biplex rapid test was favorable. However, the Ov16 RDT test may be more appropriate to use in remote areas for the point diagnosis of onchocerciasis in view towards achieving elimination in Africa.