Evaluation of diagnostic tests for human leptospirosis

The IgM-PK-ELISA, an enzyme-linked immunosorbent assay for immunoglobulin M employing a proteinase K-treated antigen, and the "Leptoteste-S" macroagglutination test were evaluated for use in a rapid serodiagnosis of human leptospirosis. The microscopic agglutination test (MAT) was used as reference. The three serological tests were applied to serum samples from patients with leptospirosis (N = 89), typhoid fever (N = 8), malaria (N = 19), syphilis (N = 20), hepatitis (N = 16) and from clinically healthy donors (N = 92). The overall results of the IgM-PK-ELISA and the "Leptoteste-S" are comparable to those of the MAT. However, both tests differed statistically from MAT in terms of the positivity of the acute-phase sera, with approximately 38% of the patients with leptospirosis being identified earlier than when MAT was used. The IgM-PK-ELISA, with 89.9% sensitivity and 97.4% specificity, could be the test of choice for those laboratories which are equipped to perform ELISA. The "Leptoteste-S", with 89.9% sensitivity and 94.8% specificity, seems to be easier to perform and the most accessible to peripheral laboratories for rapid screening of human sera. Both techniques present the important characteristic of detecting early antibodies against leptospires, thus providing a diagnosis during the early stages of the disease.