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Be Canadian – Order Fewer Head CTs

February 15, 2017

Short Attention Span Summary

Canadians…why are they so smart?
This study found that according to the Canadian CT Head Rule (CCHR), we are over-ordering CT scans on head injured patients.  In this chart review from southern California, over 27,000 trauma head CT scans were performed from 2008-2013.  A CT scan could have been avoided in 37% of these patients by properly applying the CCHR.  Of scans classified as avoidable, 13 patients (0.1%) would have been missed, as they ultimately needed a neurosurgical intervention.  When they drilled down on the 13 patients who would have been “missed” by CCHR, they were actually misclassified by cursory electronic health record review and would not have been missed.  The only problem I have is that the CCHR is hard to recall, but that’s why we have MDCalc to the rescue!

Spoon Feed
Though it’s hard to admit that my pals to the north are smarter than me, it’s true.  Proper application of the CCHR could have reduced CT utilization by 37% without missing any injuries requiring surgical intervention.


Acad Emerg Med. 2017 Jan;24(1):22-30. doi: 10.1111/acem.13061.

Computed Tomography Use for Adults With Head Injury: Describing Likely Avoidable Emergency Department Imaging Based on the Canadian CT Head Rule.

Sharp AL1,2, Nagaraj G3, Rippberger EJ1, Shen E1, Swap CJ3, Silver MA3, McCormick T4, Vinson DR5,6, Hoffman JR7.

Author information:

1Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA.

2Department of Emergency Medicine, Los Angeles Medical Center, Kaiser Permanente Southern California, Los Angeles, CA.

3Department of Emergency Medicine, San Diego Medical Center, Kaiser Permanente Southern California, San Diego, CA.

4Department of Emergency Medicine, Harbor-UCLA Medical Center, Torrance, CA.

5Department of Emergency Medicine, Kaiser Permanente Sacramento Medical Center, Sacramento, CA.

6The Permanente Medical Group and Kaiser Permanente Division of Research, Oakland, CA.

7Department of Emergency Medicine, University of California, Los Angeles, CA.



Millions of head computed tomography (CT) scans are ordered annually, but the extent of avoidable imaging is poorly defined.


The objective was to determine the prevalence of likely avoidable CT imaging among adults evaluated for head injury in 14 community emergency departments (EDs) in Southern California.


We conducted an electronic health record (EHR) database and chart review of adult ED trauma encounters receiving a head CT from 2008 to 2013. The primary outcome was discordance with the Canadian CT Head Rule (CCHR) high-risk criteria; the secondary outcome was use of a neurosurgical intervention in the discordant cohort. We queried systemwide EHRs to identify CCHR discordance using criteria identifiable in discrete data fields. Explicit chart review of a subset of discordant CTs provided estimates of misclassification bias and assessed the low-risk cases who actually received an intervention.


Among 27,240 adult trauma head CTs, EHR data classified 11,432 (42.0%) discordant with CCHR recommendation. Subsequent chart review showed that the designation of discordance based on the EHR was inaccurate in 12.2% (95% confidence interval [CI] = 5.6% to 18.8%). Inter-rater reliability for attributing CCHR concordance was 95% (κ = 0.86). Thus, we estimate that 36.8% of trauma head CTs were truly likely avoidable (95% CI = 34.1% to 39.6%). Among the likely avoidable CT group identified by EHR, only 0.1% (n = 13) received a neurosurgical intervention. Chart review showed none of these were actually “missed” by the CCHR, as all 13 were misclassified.


About one-third of head CTs currently performed on adults with head injury may be avoidable by applying the CCHR. Avoidance of CT in such patients is unlikely to miss any important injuries.

© 2016 by the Society for Academic Emergency Medicine.

PMID: 27473552 [PubMed – in process]

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