Meningitis with a negative cerebrospinal fluid Gram stain in adults: risk classification for an adverse clinical outcome.

OBJECTIVE

To derive and validate a risk score for an adverse clinical outcome in adults with meningitis and a negative cerebrospinal fluid (CSF) Gram stain.

PATIENTS AND METHODS

We conducted a retrospective study of 567 adults from Houston, Texas, with meningitis evaluated between January 1, 2005, and January 1, 2010. The patients were divided into derivation (N=292) and validation (N=275) cohorts. An adverse clinical outcome was defined as a Glasgow Outcome Scale score of 4 or less.

RESULTS

Of the 567 patients, 62 (11%) had an adverse clinical outcome. A predictive model was created using 3 baseline variables that were independently associated with an adverse clinical outcome (P<.05): age greater than 60 years, abnormal findings on neurologic examination (altered mental status, focal neurologic deficits, or seizures), and CSF glucose level of less than 2.4975 mmol/L (to convert CSF glucose to mmol/L, multiply by 0.05551). The model classified patients into 2 categories of risk for an adverse clinical outcome--derivation sample: low risk, 0.6% and high risk, 32.8%; P<.001; and validation sample: low risk, 0.5% and high risk, 21.1%; P<.001.

CONCLUSION

Adults with meningitis and a negative CSF Gram stain can be accurately stratified for the risk of an adverse clinical outcome using clinical variables available at presentation.