Estimates of C. immitis infection by skin test reactivity in an endemic community.

This report is a comparison of two delayed hypersensitivity skin test reagents, coccidioidin and Spherulin, available for detection of prior infection by Coccidioides immitis. Coccidioidin proved to be a somewhat more sensitive reagent (33.4 per cent positive, vs 29.6 per cent for Spherulin). This difference persisted in the subjects when grouped by age, sex, exposure history, or history of coccidioidomycosis. Skin test reactivity to both reagents declined with age. Independent of exposure history coccidioidin detected 7.3 per cent of the subjects who were not detected by Spherulin; Spherulin detected prior infection in only 3.5 per cent of the subjects not detected by coccidioidin. These results differ from those of previously reported studies.