Our suggested approach to determining the need for empiric antibiotic therapy in children with CSF pleocytosis*

CSF: cerebrospinal fluid; LP: lumbar puncture; BMS: bacterial meningitis score; ANC: absolute neutrophil count; PCR: polymerase chain reaction; WBC: white blood cell; MSE: meningitis score for emergencies; CRP: C-reactive protein.
* The definition of CSF pleocytosis differs in young infants versus older infants and children. In young infants (1 to 3 months of age), a CSF WBC count >9/microL is considered abnormal; in children and infants >3 months of age, a CSF WBC count >6/microL is abnormal. Refer to separate UpTo Date topics on meningitis in children for additional details of CSF interpretation, including interpreting traumatic LPs and LPs in children pretreated with antibiotics.
¶ The BMS^[1] is the most well-studied and most commonly used clinical prediction rule for bacterial meningitis. The MSE^[2] is an alternate tool that can be used in conjunction with the BMS to improve the sensitivity, specificity, and negative predictive value. The MSE assigns points for the following variables: serum procalcitonin >1.20 ng/mL (3 points), serum CRP >40 mg/L (1 point), CSF ANC >1000/mcL (1 point), CSF protein >80 mg/dL (2 points). If both scores are 0, the patient can be classified as "very low risk". If it is not possible to determine the MSE (eg, because serum CRP or procalcitonin levels were not measured or not available), the BMS can be used alone.
Δ Factors that may suggest Lyme meningitis include living in or recent travel to an endemic area, preceding tick bite and/or erythema migrans, prolonged duration of symptoms (>7 days), and the presence of a facial nerve palsy. Refer to separate UpToDate content on Lyme meningitis for additional details.
◊ Important considerations include the age and clinical status of the child, season (ie, likelihood of enteroviral infection), exposure history, and findings of the initial evaluation. In view of the serious consequences of delayed treatment for bacterial meningitis, the threshold to initiate empiric antibiotic therapy should be relatively low.