CSF CRP Testing Proven Effective for Bacterial Meningitis Detection

Timely diagnosis of bacterial meningitis is essential to reduce the risk of severe complications and mortality. Recognizing this clinical urgency, researchers at Amsterdam UMC have evaluated the use of C-reactive protein (CRP) in cerebrospinal fluid (CSF) as a diagnostic marker. Their study confirms that CRP, an inflammatory protein typically measured in blood, also provides reliable diagnostic information when tested in CSF samples.

By adapting existing laboratory infrastructure to measure CRP levels in CSF, this approach offers clinicians a rapid and cost-effective tool for distinguishing bacterial meningitis from other central nervous system (CNS) conditions. This is particularly relevant in emergency settings where timely clinical decisions are critical.

Diagnostic Accuracy and Implementation

Traditional methods for diagnosing bacterial meningitis—such as culture and PCR—can be time-consuming and may delay appropriate treatment. The CRP in CSF test demonstrated strong diagnostic performance across three patient cohorts: Danish adults, Dutch children, and a clinical implementation group in the Netherlands.

Key findings include:

• Danish adult cohort: Sensitivity of 85%, specificity of 96%, AUC of 0.92

• Pediatric cohort: Sensitivity of 94%, specificity of 98%, AUC of 0.95

• Clinical implementation cohort: Sensitivity of 100%, specificity of 94%, AUC of 0.99

These values were based on a predefined CRP cut-off of 0.3 mg/L in CSF. Notably, the test maintained high diagnostic accuracy even in patients with low CSF leukocyte counts, where traditional markers may be inconclusive.

Furthermore, combining CSF CRP levels with CSF leukocyte counts improved diagnostic accuracy across all study groups, with a pooled area under the curve (AUC) of 0.98.

Clinical Implications

The study supports incorporating CSF CRP testing into routine diagnostic protocols for patients with suspected CNS infections. Results are typically available within 30 to 60 minutes after lumbar puncture, enabling faster clinical decision-making. The test’s affordability—approximately €5 per sample—and compatibility with standard laboratory equipment further enhance its practicality.

Although the study did not measure patient outcomes directly, the authors note that CRP testing in CSF may support earlier targeted treatment decisions and help reduce unnecessary use of broad-spectrum antibiotics by improving diagnostic clarity.

Measuring CRP in CSF represents a valuable enhancement to diagnostic protocols for bacterial meningitis. Offering high sensitivity and specificity with rapid turnaround and low cost, the test is well-suited for emergency and routine clinical settings. Its successful implementation at Amsterdam UMC suggests potential for broader use in laboratories already equipped for CRP blood testing, helping facilitate more accurate and timely diagnosis of this life-threatening condition.