ArticlesThe Canadian CT Head Rule for patients with minor head injury
Introduction
An estimated one million cases of head injury are seen yearly in North American emergency departments and most are classified as minimal or minor.1 Patients with minimal head injuries have not suffered loss of consciousness or amnesia and rarely require admission to hospital. Minor head injury is defined as a patient with a history of loss of consciousness, amnesia, or disorientation and a Glasgow Coma Scale (GCS) score of 13–15.2 Although most patients with minor head injury can be discharged without sequelae after observation, a small proportion deteriorate and require neurosurgicalinter vention for intracranial haematoma.3, 4 Early diagnosis of intracranial haematoma by computed tomography (CT) followed by early surgery is very important in the treatment of such patients.
Use of CT for minor head injury has become increasingly common, particularly in North America. In 1992, an estimated 270 000 CT scans of the head were done in US emergency departments for head injury.5 Typical US hospital charges for unenhanced CT range from US$500 to 800, suggesting a national total cost of US$135–216 million. The US yield of CT for intracranial lesions in minor head injury is estimated to be quite low (0·7–3·7%).6, 7 We have previously shown a four-fold variation among similar Canadian teaching hospitals in the use of CT for minor head injury.8 More selective use of this expensive high technology investigation for patients with minor head injury could lead to large reductions in health-care costs throughout the western world.
Current guidelines provide conflicting recommendations for use of CT and previous studies to develop guidelines have been methodologically weak and inconclusive. There is a clear need for valid and reliable guidelines to allow physicians to be more selective in their use of CT without compromising care of patients with minor head injury. Clinical decision (or prediction) rules attempt to reduce the uncertainty of medical decisionmaking by standardising collection and interpretation of clinical data.9, 10 These decision-making tools are derived from original research and incorporate three or more variables from the history, physical examination, or simple tests. We have previously developed decision rules to allow physicians to be more selective in the use of radiography for patients with ankle,11, 12 knee,13 and cervical spine injuries. We aimed to prospectively derivean accurate, reliable, and clinically sensible decision rule for the use of CT in patients with minor head injury.
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Study setting and population
We undertook a prospective cohort study in ten Canadian community and teaching institutions and enrolled consecutive adult patients if they presented to one of the emergency departments after sustaining acute minor head injury. Eligibility was based upon the patients having all of the following: blunt trauma to the head resulting in witnessed loss of consciousness, definite amnesia, or witnessed disorientation; initial emergency department GCS score of 13 or greater as determined by the
Results
Between October, 1996, and December, 1999, 3121 patients were enrolled and 100% of these had complete assessment of the primary outcome measure, need for neurological intervention (Table 1, Table 2). We scanned 2078 (67%) patients to assess the secondary outcome measure, clinically important injury on CT. The remaining 33% patients, who were all discharged directly from the emergency department, underwent the structured 14-day telephone proxy outcome measure administered by a registered nurse.
Discussion
We have successfully developed a highly sensitive clinical decision rule for the use of CT in patients with minor head injuries. This rule would allow doctors in emergency departments to order CT for their patients based upon strong evidence and to provide consistent management without jeopardising optimum patient care. Patients with minor head injuries can be identified at two levels of risk. Those patients with any one of five high-risk factors are at substantial risk for requiring
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