Predictors of bacterial meningitis in the era after Haemophilus influenzae

Objective: To determine if, in the era after Haemophilus influenzae type b, the cerebrospinal fluid (CSF) white blood cell (WBC) count can be safely u sed to stratify children suspected of having bacterial meningitis into low- and high-risk groups. Design: Retrospective analysis of CSF samples. Setting: Tertiary care pediatric center in Toronto Ontario, between January 1, 1992, and October 1, 1996. Patients: All CSF samples collected on children aged 2 months to 17 years w ere included. The final database consisted of 1617 atraumatic samples from children without prior neurologic or immunologic disease who underwent a lu mbar puncture to assess the possibility of community-acquired bacterial men ingitis. Main Outcome Measures: The predictive values of CSF WBC count, differential , protein, and glucose. Results: There were 44 cases of bacterial meningitis. Five had 3 CSF WBCs p er microliter or less, and 6 had 4 to 30 CSF WBCs per microliter. The negat ive predictive value of CSF specimens with 30 WBCs per microliter or less f or bacterial meningitis was 99.3%. Cerebrospinal fluid samples with greater than 30 WBCs per microliter had a likelihood ratio for bacterial meningiti s of 10.3 (95% confidence interval, 8.0-13.1) and a positive predictive val ue of 22.3%. Other significant predictors of bacterial meningitis included age, CSF glucose, protein, gram stain, CSF-serum glucose ratio, and periphe ral blood band count. Conclusions: Given the occurrence of bacterial meningitis in children in th e absence of CSF pleocytosis, other factors should be considered when manag ing children with suspected bacterial meningitis. Children older than 6 mon ths with 30 CSF WBCs per microliter or less are at low risk for bacterial m eningitis. If clinically stable and without other laboratory markers of bac terial meningitis, hospital admission and empiric antibiotic therapy may be unwarranted.