BACKGROUND: Every year more than 2 million adults present to emergency departments in the United States with acute head trauma. Only 6% to 9% of those with apparently minor injury have an intracranial lesion by computed tomography (CT), and less than 1% will require neurosurgical intervention.1 This study develops and validates a clinical prediction guide for identifying patients with minor head injury who do not require a head CT.
POPULATION STUDIED: The study took place at a large inner city level 1 trauma center. All patients were aged at least 3 years and presented within 24 hours of a minor head injury. Minor head injury was defined as any loss of consciousness (witnessed, reported, or unknown) with a normal neurological examination and a Glasgow Coma Scale score of 15 with or without isolated deficits in short-term memory. Patients were excluded if they refused CT, had concurrent injuries precluding CT, or reported no loss of consciousness. The mean age was 36 years, and 65% were men.
STUDY DESIGN AND VALIDITY: This is a prospective validation of a clinical prediction guide. In phase 1 demographic data, symptoms, and physical findings were recorded for 520 consecutive patients with minor head injury. All of the study patients subsequently underwent CT of the head. Clinical criteria were correlated with CT findings, and a set of 7 findings was found that identified all patients with a positive CT. In phase 2, this set of 7 findings was prospectively validated in a group of 909 consecutive patients with minor head injury. The patients were analyzed in 2 groups: those who had at least one of the 7 findings and those who had none. Emergency medicine residents performed the clinical evaluations under faculty supervision. A second physician repeated the evaluation for 50 patients with 92% agreement (k=0.78). Staff neuroradiologists interpreted CT results, although it is a limitation of the study that the radiologists were apparently not blinded to the clinical condition of patients. An independent staff radiologist who was unaware of the original interpretations reviewed 50 randomly selected CT scans with 98% agreement (k=0.94). The rate of positive CT in each phase (6.9% and 6.3%, respectively) was consistent with previous studies.
OUTCOMES MEASURED: The primary outcome was the negative predictive value of the clinical prediction guide for the presence of significant head injury.
RESULTS: The following 7 findings identified all patients with a positive CT: (1) posttraumatic head pain, (2) posttraumatic emesis, (3) older than 60 years, (4) drug or alcohol intoxication, (5) deficits in short-term memory, (6) physical evidence of trauma above the clavicles, and (7) seizure. In phase 2 of the study the absence of all 7 of these findings had a negative predictive value for a positive CT of 100% (95% confidence interval, 99%-100%). Application of this clinical prediction guide to the 909 patients in phase 2 would have reduced the use of head CT by 22% without missing any abnormalities. This study did not have the power to evaluate the association seen in previous studies between coagulopathy and a positive head CT.
The authors of this study present compelling evidence that head CT is not needed for minor head injury in patients with none of the 7 findings listed. One unnecessary CT would be prevented for every 5 patients evaluated using this clinical decision rule. Based on previous studies, physicians should also obtain a CT on any patient with a coagulopathy. Given the potential for harm if the rule is inaccurate, it should be validated in another study before widespread use.