Cerebrospinal fluid C-reactive protein to diagnose healthcare-associated meningitis after neurosurgical procedures: An exploratory retrospective diagnostic accuracy study.

Introduction: Neurosurgical procedures are frequently complicated by postoperative meningitis. Current diagnostic methods are insufficient and time-consuming. Cerebrospinal fluid C-reactive protein (CSF CRP) has shown excellent diagnostic accuracy for patients with a community-acquired meningitis and can be determined quickly. Research question: This study investigates the diagnostic accuracy of CSF CRP for detecting postoperative meningitis. Materials and methods: We performed a retrospective monocenter cohort study, including patients in whom a postoperative meningitis was suspected within 30 days after neurosurgery. To assess the diagnostic accuracy of CSF CRP, the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), receiver operating curve (ROC) and area under the curve (AUC) with 95% confidence interval (CI) were calculated. Results: Forty-five patients were included of whom 8 (18%) were diagnosed with postoperative meningitis. Two of eight patients (25%) with a meningitis had a detectable CSF CRP concentration (>0.30 mg/L) compared to eighteen of 37 (49%) without a meningitis. With a cut-off value of 0.30 mg/L, CSF CRP had a 25% sensitivity, 51% specificity, 10% PPV and 76% NPV. The AUC was 0.43 (95% CI 0.22-0.66). Discussion and conclusion: The diagnostic accuracy of CSF CRP to diagnose a postoperative meningitis is poor and treatment decisions should not be based on this parameter.