title: Atraumatic headache in US emergency departments: recent trends in CT/MRI utilisation and factors associated with severe intracranial pathology.
abstract: OBJECTIVE
  To estimate recent trends in CT/MRI utilisation among patients seeking emergency care for atraumatic headache in the USA and to identify factors associated with a diagnosis of significant intracranial pathology (ICP) in these patients.
  
  
  METHODS
  Data were obtained from the USA National Hospital Ambulatory Medical Care Survey of emergency department (ED) visits between 1998 and 2008. A cohort of atraumatic headache-related visits were identified using preassigned 'reason-for-visit' codes. Sample visits were weighted to provide national estimates.
  
  
  RESULTS
  Between 1998 and 2008 the percentage of patients presenting to the ED with atraumatic headache who underwent imaging increased from 12.5% to 31.0% (p < 0.01) while the prevalence of ICP among those visits decreased from 10.1% to 3.5% (p < 0.05). The length of stay in the ED was 4.6 h (95% CI 4.4 to 4.8) for patients with headache who received imaging compared with 2.7 (95% CI 2.6 to 2.9) for those who did not. Of 18 factors evaluated in patients with headache, 10 were associated with a significantly increased odds of an ICP diagnosis: age ≥ 50 years, arrival by ambulance, triage immediacy <15 min, systolic blood pressure ≥ 160 mm Hg or diastolic blood pressure ≥ 100 mm Hg and disturbance in sensation, vision, speech or motor function including neurological weakness.
  
  
  CONCLUSIONS
  The use of CT/MRI for evaluation of atraumatic headache increased dramatically in EDs in the USA between 1998 and 2008. The prevalence of ICP among patients who received CT/MRI declined concurrently, suggesting a role for clinical decision support to guide more judicious use of imaging.
authors.affiliation: Yale School of Medicine, Attn: Hilmer Ayuso, 464 Congress Avenue Suite 260, New Haven, CT 06519, USA. john.gilbert@yale.edu
authors.forename: John W
authors.initials: JW
authors.lastname: Gilbert
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Johnson
authors.forename: Gregory L
authors.initials: GL
authors.lastname: Larkin
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Moore
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001927:Brain Diseases / Q000453:epidemiology; D015331:Cohort Studies; D004636:Emergency Service, Hospital / Q000639:trends*; D005260:Female; D006261:Headache / Q000175:diagnosis*; D006801:Humans; D007902:Length of Stay; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D015995:Prevalence; D012307:Risk Factors; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data; D014481:United States / Q000453:epidemiology; D055815:Young Adult