The sensitivities of different immunoassays for detecting leptospiral antigen.

The detection of leptospiral antigen in biological fluids is important for the diagnosis of leptospirosis in animals and man. However the sensitivity of dark field microscopy, the usual detection method, is often inadequate. A comparison was made between the sensitivities of several immunological techniques for detecting Leptospira interrogans serovar hardjo. By staphylococcal coagglutination 10(8) leptospires per ml could be detected and by countercurrent immunoelectrophoresis 10(7) per ml. The best sensitivity obtained by enzyme-linked immunosorbent assay was 10(5) leptospires per ml, and by radioimmunoassay 10(4) to 10(5) per ml. Radioimmunoassay offers the prospect of improved diagnosis of leptospirosis through the detection of leptospiral antigen.