[Meningitis with direct negative bacteriological examination. Prospective assessment of a decision making tree]. / Méningites à examen bactériologique direct négatif. Evaluation prospective d'un arbre décisionnel.

OBJECTIVE: Elaboration of a decision-making tree for differential diagnosis of bacterial and viral meningitis, when initial Gram's staining is negative. Method One-Year prospective study in an adult emergency department. Comparison with the immediately-preceding period. RESULTS: 56 patients were included. Only 4 bacterial meningitis, but none misdiagnosed. 86% sensitivity and 83% specificity for viral meningitis (n=40). Rate of patients hospitalised more than 24 hours decreasing from 62.5 to 41% (p=0.05). Antibiotic chemotherapy decreasing from 55 to 16% (p<0.001). CONCLUSION: This decision-making tree safely allows emergency differentiation between bacterial and viral meningitis, when initial Gram's staining is negative. It consequently leads to decreased rates of useless hospitalisations and antibiotic treatments. We believe that this method can be helpful during outbreaks of viral meningitis.