Evaluation of a microtiter latex agglutination test for histoplasmosis

Experiments were designed to evaluate a Microtiter latex agglutination (Micro-LA) test, as a serological aid in the diagnosis of histoplasmosis, and to compare this test with the conventional microtiter-complement fixation (CF) test for histoplasmosis. Sera tested were from cases of acute and chronic pulmonary and disseminated histoplasmosis, as well as from individuals not having histoplasmosis. Ninety-seven percent of the cases of acute pulmonary histoplasmosis had positive Micro-LA tests, whereas 91% had positive CF tests. Ninety-six percent of the patients having chronic pulmonary histoplasmosis showed positive Micro-LA tests and 91% had positive CF tests. In contrast, 64% of the cases of disseminated histoplasmosis had positive Micro-LA tests, whereas 82% had positive CF tests. None of these differences was statistically significant. Although there were no significant differences in complement fixing and agglutinating antibody cross-reactivity with Blastomyces antigens, more patients demonstrated CF titers than Micro-LA titers. Sera from patients with acute and chronic histoplasmosis showed higher Micro-LA titers than CF titers, whereas sera from cases of disseminated histoplasmosis showed higher CF titers. Histoplasmin skin testing has less of a boosting effect on agglutinating antibodies than on CF antibodies to histoplasmin. Anticomplementary sera can be used in the Micro-LA test. This test is simple to perform, and results can be obtained in 2 to 4 hr.