MACROSCOPIC AGGLUTINATION-TEST FOR RAPID DIAGNOSIS OF HUMAN LEPTOSPIROSIS

A commercially available slide agglutination test (SAT) for the diagno sis of human leptospirosis was evaluated by comparing it to an immunog lobulin M (IgM) enzyme-linked immunosorbent assay (ELISA) and to the m icroscopic agglutination test (MAT), For all 108 patients, leptospiros is was diagnosed on the basis of a fourfold or greater increase in tit er by MAT (seroconversion), and all but 1 of 245 controls were MAT neg ative (titers, <1:100), Both SAT and the IgM ELISA failed to detect on e case of infection (sensitivity, 99%), Only 3 of 145 blood donors and none of the 100 patients with other illnesses were SAT positive (spec ificity, 99%), The overall results were similar for the three tests; h owever, SAT and ELISA were statistically more sensitive as initial scr eening tests, For 22% of the patients, the diagnosis of leptospirosis was made earlier by SAT than by MAT, SAT detected 27 (44%) of 62 MAT-n egative patients with the first serum sample. ELISA and SAT had very s imilar results. Follow-up of patients for 1 year after the onset of sy mptoms showed a decreasing rate of positivity by SAT from the third mo nth on. The rate of positivity by ELISA decreased more slowly, to abou t 67% by the end of the study, By MAT all patients were persistently r eactive. SAT and ELISA seem to be convenient methods for the rapid and early screening for leptospirosis and could replace the less sensitiv e MAT. ELISA gives less subjective results than SAT and provides infor mation on IgM kinetics, but it can be performed only by the more sophi sticated laboratories. SAT is inexpensive, can be performed more quick ly and more easily than ELISA, and could be used by the less well equi pped laboratories.