Cryptococcal Antigen Testing in an Integrated Medical System: Eastern Wisconsin

Abstract

Cryptococcosis is a serious environmentally acquired endemic fungal infection commonly associated with immunocompromised hosts. Little is known regarding frequency or distribution in Wisconsin. We explored the geodemographic and clinical features of patients tested with cryptococcal antigen tests (CrAg) - previously shown to be >90% sensitive and >90% specific - within a large health care system located in eastern Wisconsin. To examine this, we retrospectively analyzed 1465 CrAg tests on 1211 unique patients (female: 50.2%; white race: 73.9%; mean age: 53.7 ± 16.5 years). At least one CrAg result was positive in 23 of 1211 patients (1.9%). From these, 21 of 23 were immunocompromised. Positive patients were disproportionately male (82.6%) and nonwhite (3.8% of those tested vs 1.2% of whites tested); P<0.01 for both. These associations remained in multivariable models. Positive patients were not significantly older (59.1 vs 53.6 years; P=0.07). Overall, 17 separate zip codes had at least one positive case. Positive patients were more prevalent in the zip codes that included the city of Milwaukee (11 of 377 [2.9% of those tested] vs 12 of 834 [1.4% of all those tested in the remaining area of the state]), but this difference was not statistically significant. No other case clustering or close proximity to waterways was observed (41% were <162 m from green space, similar to historical controls). Overall, male sex, nonwhite race/ethnicity, and immunocompromised status, not zip code, were statistically associated with positive CrAg.