Reevaluation of diagnostic histoplasma serologies

There are few quantitative guidelines for the interpretation of serologic tests for histoplasmosis. Furthermore, guidelines that have been proposed are not accepted generally. This report reviews experiences with complement fixation and latex agglutination tests performed in a large acute-care hospital in an endemic area, and depicts the relationship between the proportion of false-positive reactions and the titer at which the serologic tests were reactive. We noted a considerable number of false-positive reactions for these widely-used tests. Use of a battery of standard tests for histoplasmosis resulted in a 90% decrease in false-positive reactions. Reliance upon multiple positive results in such a battery of tests would result in failure to detect 50% of cases of disseminated histoplasmosis, but would eliminate most false positives.