Evaluation of the Leptocheck-WB IgM Rapid Test for Acute Leptospirosis Among Acute Undifferentiated Fever Patients in Hoima, Western Uganda: Very Low Sensitivity in a Setting Where Non-Icterohaemorrhagiae Leptospira Serogroups Predominate

Leptospirosis contributes substantially to acute undifferentiated fever (AUF) in sub-Saharan Africa but is underdiagnosed. Rapid diagnostic tests could enable early detection, yet the Leptocheck-WB has not been evaluated in Africa. We evaluated the Leptocheck-WB IgM rapid test in AUF patients at two health facilities in Hoima District, western Uganda (November 2023 to December 2024). Acute leptospirosis was defined by a composite reference standard combining lipL32 real-time PCR on blood and urine and the microscopic agglutination test (MAT) on paired sera. Two production batches were tested on acute-presentation whole blood and serum. Accuracy estimates carry exact binomial confidence intervals. Of 330 participants, 89 (27.0%, 95% CI 22.5–32.0) had leptospirosis. The first batch detected one of 89 cases (sensitivity of 1.1%, 0.03–6.1), and the second one detected two (2.2%, 0.3–7.9). Neither batch produced a false positive among 241 non-cases (specificity of 100%, 98.5–100). The test was negative in all 40 participants who were MAT-seropositive at presentation, including two with titres of 1:1600, while high-titre control sera reacted as expected. Across the 89 cases, MAT reactivity was dominated by the serogroup Bataviae (60 cases), followed by Australis (15) and Tarassovi (11), while Icterohaemorrhagiae was recorded in one case only, at a titre of 1:200. Sensitivity this low makes the test unsuitable for the screening or surveillance of acute leptospirosis in this setting. Limited cross-reactivity between the kit antigen and locally circulating strains is a plausible explanation that this study was not designed to test.