Evaluation of CSF variables as a diagnostic test for bacterial meningitis

Specific aetiological diagnosis of bacterial meningitis (BM) in developing countries is often difficult. Frequently, differentiating BM from viral and TB meningitis is not easy. A study was carried out with the easily and quickly performed CSF morphological and biochemical changes as a diagnostic test against the gold standard of CSF culture and/or the latex agglutination test (LAT). Children between 2 months and 11 years of age, suspected to have acute meningitis, were prospectively recruited. CSF cell count and morphology, Gram stain, culture, and protein and sugar estimations were carried out as per standard procedures. The laboratory personnel were blind to the clinical details and the findings of each other. Diagnosis based on gold standard was possible in 55 out of 114 cases. With CSF polymorphs > 60 per cent and sugar < 50 per cent of blood level as constants, various levels of total cells and protein were considered for their diagnostic properties. The protein level was not useful. We found the best cut-off level of cell count for diagnosis of BM to be 300/mm3, based on the receiver operating characteristics curve, the point of maximum accuracy. These findings were validated by comparing the clinical features, CSF changes and outcome characteristics of non-confirmed cases with the above criteria with the confirmed cases; these were found to be the same except for age.(ABSTRACT TRUNCATED AT 250 WORDS)