Predictive value of intrathecal interleukin-6 for ventriculostomy-related Infection

Early diagnosis of ventriculostomy-related infection (VRI) is crucial for the early treatment and course of this disease. In neurosurgical patients the diagnostic criteria are equivocal, mostly because of bloodstained cerebrospinal fluid (CSF). The predictive value, sensitivity and specificity of intrathecal interleukin-6 (IL-6 (CSF)) has been proven for VRI compared with classical diagnostic CSF parameters, i.e. cell countCSF (CC (CSF)) and total protein (CSF).

We prospectively analyzed the daily clinical data and CSF samples of 75 neurosurgical patients with an external ventricular drainage (EVD), which had been inserted predominantly because of poor-grade subarachnoid hemorrhage (SAH). The intrathecal interleukin-6 concentrations (IL-6 (CSF)) were correlated with the clinical course and VRI incidence, as diagnosed by the classical VRI criteria (CC (CSF), total protein (CSF), clinical symptoms).

Based on classical criteria, bacterial meningitis occurred in 26.7% of patients. Patients with VRI manifested significantly (p<0.001) higher median values of IL-6 (CSF) (up to 2,000-fold increase) the day before (day -1) infection was diagnosed by conventional parameters. Using a cut-off value of IL-6 (CSF)>or=2,700 pg/ml [4,050 pg/ml after WHO standardization] on day -1, the relative risk for VRI was 6.09 (95% CI: 2.62-14.18%). A predictive value of IL-6 (CSF)>or=2,700 pg/ml [4,050 pg/ml] for VRI was calculated of 89% (95% CI: 79.6-98.0%), a sensitivity of 73.7% and a specificity of 91.4%. The amount of intrathecal blood was an independent risk factor for VRI occurrence, whereas the mean duration of EVD in place showed no impact on the rate of infection.

Our data indicate that IL-6 (CSF) is a reliable marker for predicting VRI prior to clinically manifest meningitis, one day earlier than the common diagnostic criteria of CSF infection (CC (CSF), total protein (CSF), clinical symptoms).