BACKGROUND: The PediBIRN 4-variable clinical decision rule (CDR) detects abusive head trauma (AHT) with 96% sensitivity in pediatric intensive care (PICU) settings. Preliminary analysis of its performance in Pediatric Emergency Department settings found that elimination of its fourth predictor variable enhanced screening accuracy. OBJECTIVE: To compare the AHT screening performances of the “PediBIRN-4” CDR vs. the simplified 3-variable CDR in PICU settings. PARTICIPANTS AND SETTINGS: 973 acutely head-injured children