Canadian Computed Tomography (CT) Head Rule Study

Background: Each year, Canadian emergency department physicians treat 600,000 patients with head injury. Many of these are adults with "minor head injury", i.e. loss of consciousness or amnesia and a Glasgow Coma Scale (GCS) score of 13-15. Only 6.2% of these "minor" patients have some acute injury on computed tomography (CT scan) and only 0.5% have an epidural hematoma requiring surgery. Among Canadian teaching hospital emergency departments, we have shown a fourfold variation in use of CT and that a small but important number of intracranial hematomas are missed at the first visit. This renewal application builds on previous MRC/CIHR Health Services Research Committee funded grants to determine feasibility (phase 0, MRC GR-13304D, 1995-96), develop a clinical decision rule for CT in minor head injury (phase I, MRC MT-13700, 1996-99, N=3,121), and prospectively validate this Canadian CT Head Rule (phase II, CIHR #42521, 2000-03, N=2,707), all part of the U of Ottawa Group Grant in Decision Support Techniques (CIHR 2000-143). The Canadian CT Head Rule is comprised of simple clinical variables and allows physicians to be much more accurate in their diagnosis of brain injury and will standardize the use of CT without jeopardizing patient care (The Lancet 2001). In the recently completed prospective validation (phase II), we confirmed the accuracy and reliability of the rule in 2,707 additional patients.

Objectives: The goal of phase III is to evaluate the effectiveness and safety of an active strategy to implement the Canadian CT Head Rule into physician practice. Specific objectives are to: 1) Determine clinical impact by comparing the intervention and control sites for: a) CT Head ordering rates, b) Missed neurological intervention cases, c) Missed brain injuries, d) Number of deaths, d) Length of stay in ED, and e) Patient satisfaction; 2) Determine sustainability of the impact; 3) Evaluate performance of the Canadian CT Head Rule, with regards to: a) Accuracy, b) Physician accuracy in interpretation, and c) Physician comfort and compliance with use; 4) Conduct an economic evaluation to determine the potential for cost savings with widespread implementation; 5) Conduct an exploratory psychological process evaluation to examine whether physicians' intentions and behaviours can be predicted.

Methods: We propose a matched-pair cluster design study which compares outcomes during 3 consecutive 12-month 'before', 'after', and 'decay' periods at 6 pairs of 'intervention' and 'control' sites. These 12 hospital ED sites will be stratified as 'teaching' or 'community' hospitals, matched according to baseline CT head ordering rates, and then allocated within each pair to either intervention or control groups. During the 'after' period at the intervention sites, simple and inexpensive strategies will be employed to actively implement the Canadian CT Head Rule: a) physician group discussion and consensus, b) educational initiatives (lecture, posters, pocket cards), and c) a process-of-care modification with a mandatory reminder of the Rule at the point of requisition for radiography. These outcomes will be assessed: 1) Measures of clinical impact will compare the changes from 'before' to 'after' between the intervention and control sites: a) CT Head ordering proportions (the primary analysis); b) Number of missed brain injuries; c) Number of serious adverse outcomes; d) Length of stay in ED; e) Patient satisfaction. 2) Performance of the Canadian CT Head Rule: a) Accuracy of the rule; b) Physician accuracy of interpretation; c) Physician comfort and compliance. 3) Economic evaluation measures: a) CT head rate after discharge; b) Length of stay in ED and hospital; c) Hospital admission; d) Neurological intervention; e) Number of transfers. 4) Psychological Process Evaluation: Mail surveys of physicians before and after the intervention. During the 12-month 'decay' period, implementation strategies will continue, allowing us to evaluate the sustainability of the effect. We estimate a sample size of 2,400 patients in each period in order to have adequate power to evaluate the main outcomes.

Importance: This implementation study (phase III) is an essential step in the process of developing a new clinical decision rule / guideline for health care practitioners. Phase I successfully derived the Canadian CT Head Rule and phase II confirmed the accuracy and safety of the rule and, hence, the potential for physicians to improve care. What remains unknown is the actual change in clinical behaviour that can be effected by implementation of the Canadian CT Head Rule and whether implementation can be achieved with simple and inexpensive measures. We believe that the Canadian CT Head Rule has the potential to significantly limit health care costs and improve the efficiency of patient flow in busy Canadian EDs.