Assessment of the efficacy of an IgM-elisa and microscopic agglutination test (MAT) in the diagnosis of acute leptospirosis

In a prospective study in Barbados between 1979 and 1989, 321 cases were diagnosed in 638 patients presenting at a hospital with symptoms of leptospirosis. Initial diagnosis was based on patient history and characteristic signs and symptoms. In 92 cases (29%), diagnosis was confirmed by isolation of organisms from the blood, urine, or dialysate fluid; in the remaining 229 cases (71%) diagnosis was confirmed by serology alone. Results of an IgM-ELISA and microscopic agglutination test (MAT) in cases with isolates and in non-leptospirosis cases were used to assess the sensitivity and specificity of the tests. The sensitivity of IgM detection by ELISA was 52% in the first acute-phase specimen, increasing to 89% and 93% in the second acute-phase and convalescent specimens, respectively. The specificity of the IgM-ELISA was high (greater than or equal to 94%) in all specimens. The sensitivity of the MAT was low (30%) in the first acute-phase specimen, increasing to 63% in the second acute-phase specimen and 76% in the convalescent specimen. The specificity of the MAT was greater than or equal to 97% in all specimens.