title: Missed diagnosis of subarachnoid hemorrhage in the emergency department.
abstract: OBJECTIVE
  Subarachnoid hemorrhage (SAH) can be devastating, yet its initial presentation may be limited to common symptoms and subtle signs, potentially leading to misdiagnosis. Little is known about population rates of misdiagnosis of SAH, or hospital factors that may contribute to it. We estimated the population-based rate of missed SAH among emergency department (ED) patients and examined its relationship with hospital characteristics.
  
  
  METHODS
  We studied persons admitted with a nontraumatic SAH to all Ontario hospitals over 3 years (April 2002 to March 2005). SAH was defined as missed if the patient had an ED visit related to the SAH (based on a prespecified definition) in the 14 days before admission. We examined the association between hospital teaching status and missed SAH and explored whether annual ED volume of SAH or CT availability explained this association.
  
  
  RESULTS
  Of 1507 patients diagnosed with SAH, 5.4% (95% CI, 4.3 to 6.6) had a missed diagnosis. The risk was significantly higher among patients triaged as low acuity (odds ratio 2.65; 95% CI, 1.46 to 4.80), as well as in nonteaching hospitals (adjusted odds ratio 2.12; 95% CI, 1.02, 4.44). Neither ED SAH volume nor on-site CT availability explained the effect of teaching status.
  
  
  CONCLUSIONS
  About 1 in 20 SAH patients are missed during an ED visit. Lower acuity patients are at higher risk of misdiagnosis, suggesting the need for heightened suspicion among patients with minimal clinical findings. The risk is also greater in nonteaching hospitals, but this is not explained by the annual volume of SAHs seen in the ED or access to CT.
authors.affiliation: Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Marian J
authors.initials: MJ
authors.lastname: Vermeulen
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Schull
mesh_terms: D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D003951:Diagnostic Errors / Q000706:statistics & numerical data*; D042241:Early Diagnosis; D004636:Emergency Service, Hospital / Q000592:standards*; D005260:Female; D006297:Health Services Accessibility / Q000706:statistics & numerical data; D006764:Hospitals, Community / Q000592:standards; D006784:Hospitals, Teaching / Q000592:standards; D006801:Humans; D008297:Male; D008511:Medicine / Q000592:standards; D008875:Middle Aged; D009026:Mortality / Q000639:trends; D009864:Ontario / Q000453:epidemiology; D011237:Predictive Value of Tests; D011787:Quality of Health Care / Q000706:statistics & numerical data; D012189:Retrospective Studies; D013038:Specialization; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis* / Q000401:mortality*; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data; D014218:Triage / Q000592:standards; D000078329:Workforce; D016526:Workload / Q000706:statistics & numerical data