A risk score for identifying patients at a low risk of bacterial meningitis amongst adults with cerebrospinal fluid leucocytosis and a negative gram stain result: a derivation and validation study

Objectives: We aimed to derive and validate a risk score to differentiate patients with bacterial menin-gitis from those with viral meningitis or encephalitis amongst patients presenting with cerebrospinal fluid (CSF) leucocytosis and a negative Gram staining result.Methods: We included adults with bacterial and viral meningitis or encephalitis presenting with CSF leukocyte counts of >10 per mm3 and a negative Gram staining result from cohorts in Houston, Texas (2004-2019), and the Netherlands (2012-2021). Derivation and the first validation were performed in the American patients and further validation in the Dutch patients.Results: Derivation was performed in 109 American patients with bacterial meningitis (median age, 56 years; interquartile range [IQR], 46-66 years; 46% women) and 194 with viral meningitis or en-cephalitis (median age, 46 years; IQR, 33-60 years; 53% women). Serum leukocyte counts of >10.0 x 109/ L, CSF leukocyte counts of >2000 per mm3, granulocyte counts of >1180 per mm3, protein levels of >2.2 g/L, glucose levels of <1.9 mmol/L and fever on admission were included in the risk score, which was dichotomized into 'low risk' (0 present) and 'high risk' (>0 present). The first validation showed a sensitivity of 100% (95% CI, 96.6-100) and specificity of 34.0% (95% CI, 27.4-41.2). Further validation in 262 Dutch patients with bacterial meningitis (median age, 57 years; IQR 44-70 years; 45% women) and 68 with viral meningitis (median age, 34 years; IQR, 28-45 years; 60% women) showed a sensitivity of 99.6% (95% CI, 97.9-100) and specificity of 41.2% (95% CI, 29.4-53.7).Conclusions: Our risk score may be able to rule out bacterial meningitis amongst patients presenting with CSF leucocytosis and a negative Gram staining result. However, it needs prospective testing prior to clinical implementation. Thijs M. van Soest, Clin Microbiol Infect 2023;29:360 (c) 2022 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study aimed to establish a risk score for differentiating bacterial meningitis from viral meningitis or encephalitis in patients with cerebrospinal fluid leucocytosis and a negative Gram staining result. The effectiveness of the score was validated in cohorts from the United States and the Netherlands.