Serodiagnosis of histoplasmosis

The standard serologic tests for diagnosis of histoplasmosis include the complement fixation test (CF), which is quite sensitive, and the immunodiffusion test (ID), which is fairly specific. Radioimmunoassay (RIA) is an experimental serological test even more sensitive than CF, but also less specific. Problems with the specificity of serodiagnosis are addressed followed by a discussion of the sensitivity of the three tests in the different forms of histoplasmosis-chronic cavitary histoplasmosis, progressive disseminated histoplasmosis, and acute pulmonary histoplasmosis. Next, serologic results from a large point-source outbreak of acute pulmonary histoplasmosis in Orono, Minn, are presented. These results are used to define the sensitivity of the three tests in acute symptomatic pulmonary histoplasmosis and also to detail the time course of the appearance of antibodies measurable by each test. Finally, a case of sporadic severe acute pulmonary histoplasmosis is presented in which the approach to serodiagnosis was based on lessons learned from the Orono outbreak.