Loiasis, caused by the filarial nematode Loa loa, is endemic in Central and West Africa where about 10 million people are infected. There is a scarcity of convenient, commercial diagnostics for L. loa. Microscopy requires trained personnel and has low sensitivity, while the serodiagnosis is currently not standardized. Individual case management is also impor-tant in non-endemic countries to treat migrants, expatriates and tourists. We retrospectively compared the performance of a Loa Antibody Rapid Test (RDT) and a commercial ELISA pan-filarial test on 170 patients, 65 with loiasis [8 with eyeworm, 29 with positive microfilare-mia, 28 with neither microfilaremia nor history of eyeworm but eosinophilia and history of Calabar swelling (probable loiasis)], 95 with other common parasitic infections and no previous exposure to L. loa (37 with M. perstans, 1 with Brugia sp., 18 with strongyloidiasis, 20 with schistosomiasis, 5 with hookworm, 4 with Ascaris lumbricoides infection, 10 with hyper-reactive malarial splenomegaly), and 10 uninfected controls. The sensitivity of the RDT and of the ELISA were 93.8% (61/65) and 90.8% (59/65), respectively. For the RDT, most of the cross-reactions were observed in patients with M. perstans: 7/37 (18.9%), followed by 1/10 (10%) with hyper-reactive malarial splenomegaly and 1/20 (5%) with schistosomiasis. None of the 27 subjects infected with intestinal nematodes was found positive at this test. The ELISA is meant to be a pan-filarial assay, and reacted extensively with cases of M. perstans (95%), as expected, and also in 11/18 (61.1%) patients with strongyloidiasis and in 3/5 (60%) with hookworm infection. The RDT and the ELISA are both highly sensitive for the diagnosis of loiasis. The main difference lies in the extent of cross-reactivity with other para-sites. Considering that the RDT is specifically meant for Loa loa infection, and its high sensi-tivity, this test could be a useful tool for the diagnosis of occult loiasis. © 2020 Gobbi et al.
