title: Accuracy of physician-estimated probability of brain injury in children with minor head trauma.
abstract: OBJECTIVE
  To evaluate the accuracy of physician estimates of the probability of intracranial injury in children with minor head trauma.
  
  
  METHODS
  This is a subanalysis of a large prospective multicentre cohort study performed from July 2001 to November 2005. During data collection for the derivation of a clinical prediction rule for children with minor head trauma, physicians indicated their estimate of the probability of brain injury visible on computed tomography (P-Injury) and the probability of injury requiring intervention (P-Intervention) by choosing one of the following options: 0%, 1%, 2%, 3%, 4%, 5%, 10%, 20%, 30%, 40%, 50%, 75%, 90%, and 100%. We compared observed frequencies to expected frequencies of injury using Pearson's χ2-test in analyses stratified by the level of each type of predicted probability and by year of age.
  
  
  RESULTS
  In 3771 eligible subjects, the mean predicted risk was 4.6% (P-Injury) and 1.4% (P-Intervention). The observed frequency of injury was 4.1% (any injury) and 0.6% (intervention). For all levels of P-Injury from 1% to 40%, the observed frequency of injury was consistent with the expected frequency. The observed frequencies for the 50%, 75%, and 90% levels were lower than expected (p<0.05). For estimates of P-Intervention, the observed frequency was consistently higher than the expected frequency. Physicians underestimated risk for infants (mean P-Intervention 6.2%, actual risk 12.3%, p<0.001).
  
  
  CONCLUSIONS
  Physician estimates of probability of any brain injury in children were collectively accurate for children with low and moderate degrees of predicted risk. Risk was underestimated in infants.
authors.affiliation: *Department of Pediatrics and Child Health,University of Manitoba,Winnipeg,MB.
authors.forename: Carrie
authors.initials: C
authors.lastname: Daymont
authors.affiliation: *Department of Pediatrics and Child Health,University of Manitoba,Winnipeg,MB.
authors.forename: Terry P
authors.initials: TP
authors.lastname: Klassen
authors.affiliation: §Department of Pediatrics,University of Ottawa,ON.
authors.forename: Martin H
authors.initials: MH
authors.lastname: Osmond
mesh_terms: D000293:Adolescent; D001930:Brain Injuries / Q000000981:diagnostic imaging* / Q000209:etiology; D002648:Child; D002675:Child, Preschool; D002983:Clinical Competence; D006259:Craniocerebral Trauma / Q000150:complications / Q000000981:diagnostic imaging*; D003661:Decision Support Techniques; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D015600:Glasgow Coma Scale; D006801:Humans; D007223:Infant; D008297:Male; D011336:Probability; D011446:Prospective Studies; D012372:ROC Curve; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: decision-making; head injury; pediatrics; risk; traumatic brain injury