An Analysis of Skin Test Responses to Spherulin-Based Coccidioidin (Spherusol®) Among a Group of Subjects with Various Forms of Active Coccidioidomycosis

A reformulated skin test for coccidioidomycosis, Spherusol®, was recently approved for use in the USA. We hypothesized that it could be useful in predicting severity of illness and outcome in various types of coccidioidomycosis. Subjects with non-meningeal coccidioidomycosis attending a clinic in the coccidioidal endemic region were skin tested with Spherusol® and clinical data were collected at the time of testing and at follow-up. Twenty-seven subjects were studied, eight of whom had extrathoracic dissemination. A total of 15 subjects had positive tests, including 11 of 19 subjects with non-disseminated pulmonary disease and four with extrathoracic disseminated coccidioidomycosis. Among those with non-disseminated pulmonary disease, age ≥ 65 years, female sex, and antifungal therapy were significantly associated with a negative test on univariate but not multivariate analysis. For 23 subjects, there was a trend for those not on antifungal therapy at the time of follow-up to have a positive test but no association with coccidioidal complement-fixation titer or overall outcome. Not all subjects with non-disseminated pulmonary coccidioidomycosis were found to be skin test positive and half of those with extrathoracic disseminated disease manifested dermal hypersensitivity. In this small study, the results of the skin test were not clinically predictive of disease severity or outcome.