Immunoassay Developed for Rapid Leptospirosis Diagnosis

The rapid point-of-care immunoassay was evaluated for accuracy in diagnostic performance and compared with the microscopic agglutination test (MAT), in an urban setting.

Scientists at Duke University School of Medicine (Durham, NC, USA) and their collaborators measured the sensitivity of the assay using 446 serum samples from 378 individuals with either mild or severe leptospirosis from two urban Brazilian populations. Control sera, including healthy blood donors, dengue cases, and patients with confirmed syphilis were also tested.

The DPP assay for leptospirosis was developed by Chembio Diagnostic Systems (Medford, NY, USA) and is manufactured by Bio-Manguinhos (Rio de Janeiro, Brazil). The sera assayed by the DPP were also tested by an immunoglobulin M enzyme-linked immunosorbent assay (IgM- ELISA) and the MAT. Three independent operators visually interpreted results of the DPP after 20 minutes as either positive or negative.

The overall sensitivity for paired sera was 100% for severe and 73% for mild disease. In the acute phase of the infection, the assay achieved a sensitivity of 85% for severe and 64% for mild leptospirosis. Within seven days of illness onset, the assay achieved a sensitivity of 77% for severe disease and 60% for mild leptospirosis. Sensitivity of the DPP assay was similar to that for IgM-ELISA and increased with both duration of symptoms.

The authors concluded that the DPP assay performed acceptably well for diagnosis of severe acute clinical leptospirosis and can be easily implemented in hospitals and health posts where leptospirosis is a major public health problem. However, test accuracy may need improvement for mild disease and early stage leptospirosis, particularly in regions with high transmission. The study was published on November 1, 2012, in the journal Public Library of Science Neglected Tropical Diseases (PLoSNTD).

Related Links:
Duke University School of Medicine
Chembio Diagnostic Systems
Bio-Manguinhos