Role of Coccidioides Antigen Testing in the Cerebrospinal Fluid for the Diagnosis of Coccidioidal Meningitis

Background. Coccidioidal meningitis (CM), a common cause of chronic meningitis in endemic area, is usually diagnosed by detection of anti-Coccidioides antibodies in cerebrospinal fluid (CSF), and findings may be negative in up to one-third of cases. CSF cultures and cytology are infrequently positive. Antigen detection has been used for the diagnosis of other forms of coccidioidomycosis and meningitis caused by other mycoses. The purpose of this study was to assess the diagnostic utility of CSF Coccidioides antigen (CAg) detection for the diagnosis of CM. Methods. The medical records of patients with clinically suspected meningitis, in whom CSF was tested for Coccidioides antibodies and CAg, were retrospectively reviewed, and CSF CAg testing was prospectively conducted in patients with CM. All specimens were submitted for CAg testing. Results. Thirty-six patients with 42 episode of CM were studied. The sensitivity and specificity of CAg were 93% and 100%, respectively. Cultures of CSF were positive in 7%, antibodies were demonstrated by immunodiffusion in 67% and complement fixation in 70%, and immunoglobulin M and G antibodies were demonstrated by enzyme immunoassay in 8% and 85%, respectively. Conclusions. Testing CSF for CAg is a useful addition to diagnostic methods in suspected CM and complements testing with CSF antibodies and culture.