The following is a summary of the “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,” published in the March 2023 issue of Clinical Microbiology and Infections Disease by Soest, et al.

Patients presenting with cerebrospinal fluid (CSF) leucocytosis and a negative Gram staining result were studied to derive and validate a risk score for distinguishing bacterial meningitis from viral meningitis or encephalitis. Meningitis and encephalitis cases in adults with CSF leukocyte counts >10 per mm³ and a negative Gram staining result were included from cohorts in Houston, Texas (2004-2019) and the Netherlands (2012–2021). Patients in the United States were used for the initial validation and the derivation process.

In the United States, 109 patients with bacterial meningitis (median age 56; IQR 46-66 years; 46% women) and 194 with viral meningitis or encephalitis (median age 46; IQR 33-60 years; 53% women) were used for the derivation. The risk score was composed of the following variables: serum leukocyte count >10.0×10⁹/L, cerebrospinal fluid leukocyte count >2000 per mm³, granulocyte count >1,180 per mm³, protein level >2.2 g/L, glucose level 1.9 mmol/L, and admission fever. The first round of validation yielded a 100% sensitivity (95% CI = 96.6-100) and a 34% specificity (95% CI = 27.4-41.2). 

There was a sensitivity of 99.6% (95% CI, 97.9-100) and a specificity of 41.2% (95% CI, 29.4-53.7) in a further validation study involving 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). Patients presenting with CSF leucocytosis and a negative Gram stain result may be able to rule out bacterial meningitis using our risk score. Yet, it must undergo prospective testing before being used in a clinical setting.

Source: sciencedirect.com/science/article/abs/pii/S1198743X22005146