Evaluation of MAT, IgM ELISA and PCR methods for the diagnosis of human leptospirosis

Serum samples from 125 patients with clinical suspicion of leptospirosis were tested by the microscopic agglutination test (MAT), IgM ELISA and PCR for the diagnosis of the disease. Most patients were adult males and 74.1% (p<0.001) of the patients exposed to water and 77.6% (p<0.001) of those exposed to animals, were respectively considered confirmed or probable cases by MAT. The clinical symptoms mainly observed among the patients considered confirmed or probable cases were fever (95.6%), jaundice and headache (79.4%), myalgia (77.9%), nausea and vomiting (64.7%). About 63% of the confirmed or probable cases were patients that lived in Belo Horizonte, a big city of the Minas Gerais state, Brazil, showing the occurrence of urban leptospirosis. Among the 47 confirmed cases of leptospirosis diagnosed by MAT, 44 (94%) serum samples were positive by IgM ELISA and 17 (36%) were PCR positive. Among the 33 probable cases, 10 (30%) samples showed positive amplification by PCR. By considering MAT as the standard test, the sensitivity and specificity of IgM ELISA was 96.6% and 93.3%, respectively. A relevant finding in our study was the number of positive cases verified by PCR (13-29%) and IgM ELISA (3-7%) among the 45 unconfirmed cases by MAT, demonstrating the value of PCR in the early diagnosis of human leptospirosis.