Computed Tomography Use for Adults with Head Injury: Describing Likely Avoidable ED Imaging based on the Canadian CT Head Rule

Abstract

Background

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

Objective

To determine the prevalence of likely avoidable CT imaging among adults evaluated for head injury in 14 community emergency departments (ED) in Southern California from 2008-2013.

Methods

We conducted an electronic health record (EHR) data-base and chart review of adult ED trauma encounters receiving a head CT from 2008-2013. 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 system-wide 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.

Results

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% CI 5.6-18.8%). Inter-rater reliability for attributing CCHR concordance was 95% (kappa=0.86). Thus we estimate that 36.8% of trauma head CTs were truly likely avoidable (95% CI 34.1-39.6%). 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.

Conclusion

About 1/3 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.

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