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Predictors of bacterial meningitis in the era after Haemophilus influenzae
S B Freedman1, A Marrocco, J Pirie
1Department of Pediatrics, Faculty of Medicine, University of Toronto, Ontario.
Insights
In children, a cerebrospinal fluid (CSF) white blood cell (WBC) count of 30 or less indicates a low risk for bacterial meningitis. Other clinical factors are crucial for managing suspected cases, potentially avoiding unnecessary hospital admission and antibiotics.
Area of Science:
- Pediatrics
- Infectious Diseases
- Clinical Microbiology
Background:
- The incidence of bacterial meningitis has changed since the introduction of Haemophilus influenzae type b vaccines.
- Accurate risk stratification is essential for managing children with suspected bacterial meningitis.
Purpose of the Study:
- To evaluate the utility of cerebrospinal fluid (CSF) white blood cell (WBC) count in stratifying children with suspected bacterial meningitis into low- and high-risk groups.
- To determine if CSF WBC count alone is sufficient for risk assessment in the post-Hib vaccine era.
Main Methods:
- Retrospective analysis of 1617 atraumatic CSF samples from children aged 2 months to 17 years.
- Evaluation of predictive values for CSF WBC count, differential, protein, and glucose in diagnosing bacterial meningitis.
- Inclusion of children without prior neurologic or immunologic disease.
Main Results:
- A CSF WBC count of 30 or less had a 99.3% negative predictive value for bacterial meningitis.
- CSF samples with >30 WBCs/µL had a likelihood ratio of 10.3 for bacterial meningitis.
- Age, CSF glucose, protein, gram stain, CSF-serum glucose ratio, and peripheral blood band count were also significant predictors.
Conclusions:
- Bacterial meningitis can occur in children without CSF pleocytosis, necessitating consideration of additional factors.
- Children over 6 months with CSF WBC count ≤30/µL are generally low-risk.
- Hospital admission and empiric antibiotics may be unnecessary for stable, low-risk children without other concerning laboratory markers.
Objective:
To determine if, in the era after Haemophilus influenzae type b, the cerebrospinal fluid (CSF) white blood cell (WBC) count can be safely used 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 were included. The final database consisted of 1617 atraumatic samples from children without prior neurologic or immunologic disease who underwent a lumbar puncture to assess the possibility of community-acquired bacterial meningitis.
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 per microliter or less, and 6 had 4 to 30 CSF WBCs per microliter. The negative predictive value of CSF specimens with 30 WBCs per microliter or less for bacterial meningitis was 99.3%. Cerebrospinal fluid samples with greater than 30 WBCs per microliter had a likelihood ratio for bacterial meningitis of 10.3 (95% confidence interval, 8.0-13.1) and a positive predictive value of 22.3%. Other significant predictors of bacterial meningitis included age, CSF glucose, protein, gram stain, CSF-serum glucose ratio, and peripheral blood band count.
Conclusions:
Given the occurrence of bacterial meningitis in children in the absence of CSF pleocytosis, other factors should be considered when managing children with suspected bacterial meningitis. Children older than 6 months with 30 CSF WBCs per microliter or less are at low risk for bacterial meningitis. If clinically stable and without other laboratory markers of bacterial meningitis, hospital admission and empiric antibiotic therapy may be unwarranted.