Cumulative red flag count as a predictor of intracranial pathology in pediatric emergency headache: A threshold-based analysis.

BACKGROUND: Structured red flag assessment guides neuroimaging decisions in pediatric emergency headache. Cumulative scoring may offer greater discriminative value than individual flag analysis; however, imaging-based cohort evidence is subject to selection and spectrum bias, limiting extrapolation to unselected populations. OBJECTIVE: To evaluate 12 predefined red flags for predicting abnormal cranial neuroimaging and explore cumulative count thresholds in a pediatric emergency department (ED) imaging-based cohort. METHODS: This single-center, retrospective, cross-sectional study enrolled consecutive pediatric patients (aged 2-18 years) who underwent cranial neuroimaging for headache at a tertiary ED (January 2022 to June 2025). Twelve red flags were coded as binary variables. Diagnostic accuracy metrics and positive likelihood ratio were calculated for individual flags and cumulative thresholds. Discriminative performance was assessed using the area under the curve (AUC) with bootstrap 95% confidence intervals (CI). RESULTS: Of 187 patients (median age 14.7 years; 60% female), 14 (7.5%; 95% CI: 4.3%-11.9%) had abnormal neuroimaging. Red flag count was significantly higher in the abnormal group (median 5 vs. 1; p < 0.001). None of 54 patients with zero red flags had abnormal neuroimaging. AUC was 0.995 (95% CI: 0.985-1.000). At ≥3 flags, sensitivity and negative predictive value (NPV) were 100%; at ≥4, sensitivity was 93%, specificity 99%, and positive predictive value (PPV) 87%. CONCLUSIONS: Cumulative red flag enumeration identified risk strata with differing rates of abnormal neuroimaging in a pediatric ED imaging-based cohort. These hypothesis-generating findings are subject to selection and spectrum bias; prospective validation in unselected populations is required before clinical application.