[The Current Status of Diagnostic Tools for Leptospirosis].

Leptospirosis is a worldwide zoonosis caused by pathogenic Leptospira spp. The severity of leptospirosis vary from mild, flu-like disease to a more severe form, Weil's disease causing jaundice, hemorrhage, renal failure, and even death. Every year, 300,000‒500,000 cases of severe leptospirosis are reported around the world, with the case fatality rate being 10‒30%. The usual diagnostic tools for leptospirosis are 1) direct observation of leptospires in blood and urine under dark-field microscope, 2) isolation of leptospires from blood, cerebrospinal fluid (CSF), or urine samples by culture, 3) microscopic agglutination test (MAT) to detect anti-Leptospira antibodies in serum, and 4) PCR to detect Leptospira DNA. At presents, the gold standards for diagnosis are culture isolation and MAT. However, it is actually not easy to isolate leptospires from clinical samples. On the other hand, it takes several days before the results of MAT become positive after the onset of illness. Moreover, MAT requires skilled handling, and also needs the maintenance of live Leptospira cells representing all serogroups. Hence other simple or rapid diagnostic tests are needed at the bedside. The micro capsule agglutination test (MCAT) to detect antibody and immunochromatographic assay to detect urinary antigen are currently in the research and development phases. In this paper, the characteristics of each diagnostic test for leptospirosis are described.