External ventricular drain–related meningitis: prediction model or early diagnostic tool?

To the Editor, We read with great interest the study by Raffenot et al. on risk factors for nosocomial meningitis (NM) in patients with external ventricular drains (EVDs) [1].We commend the authors on their thorough and clinically impactful study.Their identification of factors such as cerebrospinal fluid (CSF) leakage and prolonged drainage offers valuable insight for daily practice.The authors also develop a multivariable predictive model, incorporating CSF leakage, drainage duration, beta-lactam allergy, and a combined CSF variable (glucose ratio < 0.5 and protein > 1 g/L).This model demonstrates excellent discrimination (AUC 0.89) and the authors suggest that it could help identify high-risk patients earlier and guide closer monitoring and empirical therapy.We would, however, like to highlight one methodological point central to how the model's performance and role should be understood.The authors define NM using criteria adapted from Lozier et al., in which "probable" infection is based on specific cerebrospinal fluid (CSF) abnormalities: leukocyte count > 100/mm3, CSF-to-serum glucose ratio < 0.5, and protein concentration > 0.4 g/L [1, 2].In