Identifying risk factors for an abnormal computed tomographic scan of the head among patients with altered mental status in the Emergency Department.

Aims: The aims of our study are to evaluate the use of computed tomographic scan of the head (CT-head) in patients with altered mental status (AMS) presenting to the Emergency Department (ED) and to identify clinical features associated with an abnormal CT-head result.

Methods: In this prospective observational study, we recruited consecutive adult patients with undifferentiated AMS and no major trauma at a busy urban ED over 11 months. Demographical, clinical, radiological and laboratory data were collected prospectively. The primary outcome measure was an abnormal CT-head result. Secondary outcome measures were the distribution of aetiologies of AMS with age, mortality rate and length of hospital stay. Logistic regression was applied to identify variables associated with an abnormal CT-head result.

Results: Nine hundred and sixty-seven patients were recruited. The rate of CT-head use in the ED was 41%, with 45% of the scans being abnormal. We identified eight clinical factors associated with an abnormal CT-head result. Odds ratios (95% confidence intervals) for diastolic blood pressure greater than 80 mmHg, focal weakness, Glasgow Coma Score less than 15, antiplatelet use, upgoing plantar response, presence of headache, anticoagulant use and dilated pupils were 1.016 (1.003-1.029), 1.816 (1.063-3.103), 1.899 (1.113-3.242), 2.203 (1.146-4.234), 2.680 (1.623-4.427), 3.369 (1.449-7.830), 3.589 (1.253-10.283) and 5.212 (1.153-23.558), respectively.

Conclusion: Our study identified important risk factors for an abnormal CT-head result which can be used in future research to establish a guideline for rational ordering of the test in AMS patients.