The utility of Coccidioides polymerase chain reaction testing in the clinical setting

Coccidioidomycosis, the fungal infection caused by dimorphic Coccidioides sp., is typically diagnosed by histopathologic identification of spherules in affected secretions and tissues or by culture. These tests are reliable but time-intensive, delaying diagnosis and treatment. To evaluate a polymerase chain reaction (PCR) test developed to detect Coccidioides sp. in clinical specimens, we conducted a retrospective chart review of all patients (N = 145) who underwent Coccidioides PCR at our institution between April 27, 2007, and May 6, 2008, abstracting clinical, microbiologic, serologic, radiographic, treatment, and follow-up data. One hundred fifty-eight PCR tests (153 respiratory; 5 cerebrospinal fluid) produced 5 positive and 153 negative findings. Five of nine patients (56%) with confirmed or highly probable pulmonary coccidioidomycosis had a positive PCR on respiratory specimens, and four of nine (44%) had a positive culture. Among two patients with coccidioidal meningitis, none had a positive PCR, whereas Coccidioides sp. in fungal culture grew for one of two. Among six asymptomatic patients with probable coccidioidomycosis, none had a positive culture or PCR. Compared with culture of respiratory specimens, PCR demonstrated a sensitivity, specificity, positive predictive value, and negative predictive value of 75, 99, 60, and 99%, respectively. Coccidioides PCR appears accurate in identifying negative results, and its sensitivity is similar to that of fungal culture.