Serum procalcitonin levels in patients with primary pulmonary coccidioidomycosis.

RATIONALE: The serum procalcitonin assay has emerged as a promising biomarker to distinguish between bacterial and viral respiratory tract infections but has not been used to differentiate coccidioidomycosis from bacterial infection. A correlation between procalcitonin serum levels and coccidioidomycosis has never been reported. OBJECTIVE: To determine any association between serum procalcitonin levels and primary pulmonary coccidioidomycosis. METHODS: We identified and enrolled 20 immunocompetent patients with symptomatic primary pulmonary coccidioidomycosis of < 8 weeks' duration and performed a one-time procalcitonin assay, with a cutoff of < 0.25 µg/L indicating a nonbacterial infection. MEASUREMENTS AND MAIN RESULTS: Nineteen of 20 patients (95%) had serum procalcitonin of < 0.25 µg/L. The median procalcitonin level was 0.05 µg/L (range, < 0.05-0.87 µg/L; interquartile range, 0.05-0.05 µg/L). Sixteen of 20 patients (80%) had undetectable procalcitonin of < 0.05 µg/L. The four patients with detectable procalcitonin had a median value of 0.2 µg/L (range, 0.09-0.87 µg/L). CONCLUSIONS: In this pilot study, procalcitonin was not elevated in immunocompetent patients with primary pulmonary coccidioidomycosis at a median of 32 days after symptom onset. Larger prospective studies are needed to confirm this finding.