Procalcitonin in cerebrospinal fluid in meningitis: a prospective diagnostic study

Objectives: Bacterial meningitis is a severe but treatable condition. Clinical symptoms may be ambiguous and current diagnostics lack sensitivity and specificity, complicating diagnosis. Procalcitonin (PCT) is a protein that is elevated in serum in bacterial infection. We aimed to assess the value of PCT in cerebrospinal fluid (CSF) in the diagnosis of bacterial meningitis. 

Methods: We included patients with bacterial meningitis, both community acquired and post neurosurgery. We included two comparison groups: patients with viral meningitis and patients who underwent lumbar punctures for noninfectious indications. We calculated mean differences and 95% confidence intervals of procalcitonin in CSF and plasma in patients with and without bacterial meningitis. 

Results: Average PCT concentrations in CSF were 0.60 ng mL⁻¹ (95% CI: 0.29–0.92) in the bacterial meningitis group (n = 26), 0.81 (95% CI: 0.33–1.28) in community-acquired meningitis (n = 16) and 0.28 (95% CI: 0.10–0.45) in postneurosurgical meningitis (n = 10), 0.10 ng mL⁻¹ (95% CI: 0.08–0.12) in the viral meningitis group (n = 14) and 0.08 ng mL⁻¹ (95% CI: 0.06–0.09) in the noninfectious group (n = 14). Mean difference of PCT-CSF between patients with community-acquired bacterial meningitis and with viral meningitis was 0.71 ng mL⁻¹ (95% CI: 0.17–1.25) and 0.73 ng mL⁻¹ (95% CI: 0.19–1.27) for community-acquired bacterial meningitis versus the noninfectious group. The median PCT CSF: plasma ratio was 5.18 in postneurosurgical and 0.18 in community-acquired meningitis (IQR 4.69 vs. 0.28). 

Conclusion: Procalcitonin in CSF was significantly higher in patients with bacterial meningitis when compared with patients with viral or no meningitis. PCT in CSF may be a valuable marker in diagnosing bacterial meningitis, and could become especially useful in patients after neurosurgery.