Evidence‑Based Diagnostic and Management Recommendations for Acute Meningitis

Primary CSF Diagnostic Parameters

The European Society of Clinical Microbiology and Infectious Diseases (ESCMID) recommends CSF analysis as the gold‑standard diagnostic test for meningitis, with mandatory assessment of leukocyte count, protein concentration, glucose concentration (and CSF:serum glucose ratio), and Gram stain with culture (Grade A recommendation) 3.

In pediatric patients, a serum C‑reactive protein level > 40 mg/L yields approximately 93 % sensitivity and 100 % specificity for bacterial meningitis (ESCMID) 1, 2.
C‑reactive protein loses discriminative value when other bacterial infections such as sepsis or pneumonia are present (ESCMID) 1, 4.
Serum procalcitonin is endorsed as the most validated serum biomarker for distinguishing bacterial from viral meningitis and should be used as an adjunct to CSF analysis (Praxis Medical Insights) 5.

ESCMID advises obtaining blood cultures before the first dose of antibiotics (Grade A recommendation) 3.
Blood cultures are positive in roughly 75 % of pneumococcal meningitis cases (ESCMID) 2.
Blood cultures are positive in 50–90 % of Haemophilus influenzae meningitis cases (ESCMID) 1.
Blood cultures are positive in 40–60 % of meningococcal meningitis cases (ESCMID) 1, 2.

ESCMID notes that measuring CSF lactate provides good sensitivity and specificity for differentiating bacterial from aseptic meningitis (ESCMID) 1, 3.
Cell count with differential, protein, glucose (with simultaneous serum glucose), and Gram stain/culture are required components of the lumbar puncture work‑up (ESCMID) 6, 1, 3.

ESCMID guidelines explicitly state that serum prolactin has no validated diagnostic or prognostic role in meningitis and should not be measured (ESCMID) 1.

Obtain blood cultures before initiating antimicrobial therapy (ESCMID) 3.
Perform lumbar puncture promptly and send CSF for the recommended panel (cell count, protein, glucose, Gram stain, culture, and consider lactate) (ESCMID) 6, 1, 3.
Use serum procalcitonin as an adjunctive marker, not as a stand‑alone test (Praxis Medical Insights) 5.
Do not delay antibiotic administration while awaiting laboratory results (Praxis Medical Insights) 5.

Relying solely on serum inflammatory markers (e.g., CRP, PCT) can lead to misdiagnosis because they may be elevated in non‑meningeal bacterial infections (ESCMID) 1, 4.
Using procalcitonin in isolation to decide on antimicrobial therapy is discouraged (Praxis Medical Insights) 5.
Ordering unvalidated biomarkers such as serum prolactin wastes resources and may delay appropriate care (Praxis Medical Insights) 5.
Recognize that CSF findings may be atypical in neonates, partially treated patients, or infections with specific pathogens such as Listeria (ESCMID) 6, 7.