Detection of coccidioidal antibodies by 33-kDa spherule antigen, Coccidioides EIA, and standard serologic tests in sera from patients evaluated for coccidioidomycosis

During a 9-month study of patients being evaluated for coccidioidomycosis, 1 or more serum samples were obtained from 138 patients with an illness suggestive of recent infection. In this group, standard immunodiffusion tests of unconcentrated sera were positive for 25; 49 additional patients had at least 1 reactive test result by newer enzyme- linked serologic tests. At least 11 of these 49 patients had coccidioidomycosis as determined by culture or subsequent standard serologic tests. Patients with coccidioidomycosis identified only by newer tests had fewer or milder clinical abnormalities than did patients in whom the disease was detected by standard tests. For 31 other patients with illness of a chronic or undetermined duration, newer tests detected only 10 more than the 18 identified by standard tests, suggesting that later in the course of illness, standard testing gains in sensitivity for coccidioidal infection.