KT Evidence Bite: Comparison of the Canadian CT Head Rule and the New Orleans Criteria

In Knowledge Translation by Eve Purdy2 Comments

Editor’s note: This is a series based on work done by three physicians (Patrick ArchambaultTim Chaplin, and our BoringEM Managing editor Teresa Chan)  for the Canadian National Review Course (NRC). You can read a description of this course here.

The NRC brings EM residents from across the Canada together in their final year for a crash course on everything emergency medicine. Since we are a specialty with heavy allegiance to the tenets of Evidence-Based Medicine, we thought we would serially release the biggest, baddest papers in EM to help the PGY5s in their studying via a spaced-repetition technique. And, since we’re giving this to them, we figured we might as well share those appraisals with the #FOAMed community! We have kept much of the material as drop downs so that you can quiz yourself on the studies.

Paper: Comparison of the Canadian CT Head Rule and the New Orleans Criteria in patients with minor head injury

Stiell, I. G., Clement, C. M., Rowe, B. H., Schull, M. J., Brison, R., Cass, D., … & Wells, G. A. (2005). Comparison of the Canadian CT Head Rule and the New Orleans Criteria in patients with minor head injury. Jama294(12), 1511-1518.  doi:10.1001/jama.294.12.1511.

Nickname of study: 

Summarized by: Patrick Archambault
Reviewed by: Teresa Chan & Tim Chaplin


Clinical Question

Compare the clinical performance of the Canadian CT Head Rule (CCHR) and New Orleans Criteria (NOC) decision rules for detecting the need for neurosurgical intervention and clinically important brain injury. See decision rules here.

Blunt trauma with LOC, amnesia, disorientation
GCS 13+
Injury within 24 hours

<16 years old
Minimal head injury
Penetrating injury, depressed skull fracture, focial neurological deficits, unstable vitals
Bleeding disorder or anticoagulants
InterventionApplication of CDR
ControlCT head or Outcome measure at 14 days without headache absent or mild, no complaints of memory or concentration problems, no seizure or focal motor findings, and returned to normal daily activities
OutcomeNeed for neurosurgical intervention or clinically important brain injury on CT


This is a validation and a head-to-head comparison of the previously derived rules.

Prospective cohort study in 9 Canadian ED with a 1822 patients. Both clinical decision rules were applied to patients and compared to the gold standard CT. Patients were assessed by residents or ED physicians trained with a one hour lecture and reported on standardized forms. Some independent assessments were done to assess interobserver agreement.


8 patients (0.4%) required neurosurgical intervention and 97 (5.3%) had clinically important brain injury.


  • The NOC and the CCHR both had 100% sensitivity
  • CCHR was more specific (76.3% vs 12.1%, P<.001)


  • the CCHR and the NOC had 100% sensitivity
  • the CCHR was more specific (50.6% vs 12.7%, P<.001)


  • CCHR= 52.1% would require CT vs NOC=88.0%  would require CT (P<.001).


  • The kappa values for physician interpretation of the rules, CCHR vs NOC, were 0.85 vs 0.47.


CCHR and NOC are both highly sensitive rules for ruling out significant head injuries. The CCHR has higher specificity and therefore reduces the number of CT scans ordered relative to the NOC.


Take Home Point

The Canadian CT Head Rule is a highly sensitive tool for ruling out significant head injuries.


EBM Considerations

There was the possibility of familiarity bias affecting the results that would favor the CCHR since this study was performed in Canada. Not ALL patients in the study underwent CT. Some eligible patients were not enrolled as enrollment required voluntary assessment and completion of forms by ED physicians, possibly resulting in selection bias. Some patients were lost to follow up.


To download a copy of this summary click here NRC – BoringEM – Canadian Head CT.

Eve Purdy

Senior Editor at BoringEM
Senior emergency medicine resident and anthropology student-happily consuming, sharing, creating and researching #FOAMed.
BoringEM has been 'bringing the boring' to emergency medicine since 2012. In 2016 this Canadian blog brought its content to CanadiEM.