“…While the focus of the parent study11 was on the validation of three other paediatric-specific neuroimaging rules ((i) the prediction rule for the identification of children at very low risk of clinically important traumatic brain injury developed by the Paediatric Emergency Care Applied Research Network (PECARN),6 (ii) the Canadian Assessment of Tomography for Childhood Head Injury (CATCH) rule7 and (iii) the Children’s Head Injury Algorithm for the Prediction of Important Clinical Events (CHALICE))8 published elsewhere,11 we also collected the predictor and outcome variables of the NEXUS II rule 9 10. Using the published predictor variables and ICI as outcome variable as defined by NEXUS, we assessed the accuracy (sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV)) of NEXUS II in patients in the whole cohort of patients, using systematic telephone follow-up data as a surrogate for negative primary outcome of no ICI if no CT scan had been performed.…”