Efficacy of immunoglobulin M serodiagnostic test for rapid diagnosis of acute babesiosis

To evaluate the efficacy of an immunoglobulin M indirect immunofluorescent-antibody procedure for diagnosing acute babesiosis, we tested patients with acute babesiosis from a site in New England where the disease is enzootic. The sensitivity of the test was 91%, the specificity was 99%, the positive predictive value was 86%, and the negative predictive value was 99%. This B. microti immunoglobulin M indirect immunofluorescent-antibody procedure is sufficiently sensitive, specific, and reproducible for use in the routine clinical diagnosis of acute babesiosis.