CEREBROSPINAL-FLUID INTERLEUKIN-6 AND ITS DIAGNOSTIC-VALUE IN THE INVESTIGATION OF MENINGITIS

We examined the measurement and the diagnostic value of cerebrospinal fluid interleukin-6 (CSF IL-6) in meningitis. The cytokine was measure d by bioassay (B9 hybridoma cell line) and by immunoassay (in-house ra dioimmunoassay). We compared the diagnostic value of CSF IL-6 determin ation with that of other biochemical markers of meningitis. Although t here was significant correlation between bioactive and immunoactive IL -6 (r = 0.724, P < 0.001), results were frequently different with biol ogical/immunological ratios ranging from 0.2 to 24.3 (mean 4.6). Gel p ermeation chromatography suggested that the discrepancy in biological and immunological activities was not due to molecular heterogeneity, b ut may be explained by the presence of a synergistic factor. Interleuk in-6 concentration was markedly elevated in CSF from most patients wit h bacterial meningitis compared to patients with viral meningitis and those without evidence of infection. However, low IL-6 levels by radio immunoassay did not exclude bacterial meningitis (sensitivity 86%). CS F total protein and CSF glucose were significantly different between a ll three groups, but there was no significant difference in lactate co ncentration between virally infected and normal CSF, both of which had lower lactate concentrations than those in bacterial infection. CSF I L-6 measurement had greater sensitivity, specificity and predictive va lue than these other biochemical markers, and hence a rapid assay for IL-6 in CSF may contribute to the early diagnosis of bacterial infecti on.