title: Missed strokes using computed tomography imaging in patients with vertigo: population-based cohort study.
abstract: OBJECTIVE
  The purpose of this study was to determine the proportion of emergency department (ED) patients with a diagnosis of peripheral vertigo who received computed tomography (CT) head imaging in the ED and to examine whether strokes were missed using CT imaging.
  
  
  METHODS
  This population-based retrospective cohort study assessed patients who were discharged from an ED in Ontario, Canada, with a diagnosis of peripheral vertigo, April 2006 to March 2011. Patients who received CT imaging (exposed) were matched by propensity score methods to patients who did not (unexposed). If performed, CT imaging was presumed to be negative for stroke because brain stem/cerebellar stroke would result in hospitalization. We compared the incidence of stroke within 30, 90, and 365 days subsequent to ED discharge between groups, to determine whether the exposed group had a higher frequency of early strokes than the matched unexposed group.
  
  
  RESULTS
  Among 41 794 qualifying patients, 8596 (20.6%) received ED head CT imaging, and 99.8% of these patients were able to be matched to a control. Among exposed patients, 25 (0.29%) were hospitalized for stroke within 30 days when compared with 11 (0.13%) among matched nonexposed patients. The relative risk of a 30- and 90-day stroke among exposed versus unexposed patients was 2.27 (95% confidence interval, 1.12-4.62) and 1.94 (95% confidence interval, 1.10-3.43), respectively. There was no difference between groups at 1 year. Strokes occurred at a median of 32.0 days (interquartile range, 4.0-33.0 days) in exposed patients, compared with 105 days (interquartile range, 11.5-204.5) in unexposed patients.
  
  
  CONCLUSIONS
  One fifth of patients diagnosed with peripheral vertigo in Ontario received imaging that is not recommended in guidelines, and that imaging was associated with missed strokes.
authors.affiliation: From the Division of Emergency Medicine, Department of Medicine, University of Toronto, Toronto, Ontario, Canada (K.G., C.L.A.); Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada (P.C.A., C.L.A.); University Health Network, Toronto, Ontario, Canada (M.K.K.); and the Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada (P.C.A., M.K.K., H.L., C.L.A.).
authors.forename: Keerat
authors.initials: K
authors.lastname: Grewal
authors.affiliation: From the Division of Emergency Medicine, Department of Medicine, University of Toronto, Toronto, Ontario, Canada (K.G., C.L.A.); Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada (P.C.A., C.L.A.); University Health Network, Toronto, Ontario, Canada (M.K.K.); and the Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada (P.C.A., M.K.K., H.L., C.L.A.).
authors.forename: Peter C
authors.initials: PC
authors.lastname: Austin
authors.affiliation: From the Division of Emergency Medicine, Department of Medicine, University of Toronto, Toronto, Ontario, Canada (K.G., C.L.A.); Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada (P.C.A., C.L.A.); University Health Network, Toronto, Ontario, Canada (M.K.K.); and the Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada (P.C.A., M.K.K., H.L., C.L.A.).
authors.forename: Moira K
authors.initials: MK
authors.lastname: Kapral
authors.affiliation: From the Division of Emergency Medicine, Department of Medicine, University of Toronto, Toronto, Ontario, Canada (K.G., C.L.A.); Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada (P.C.A., C.L.A.); University Health Network, Toronto, Ontario, Canada (M.K.K.); and the Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada (P.C.A., M.K.K., H.L., C.L.A.).
authors.forename: Hong
authors.initials: H
authors.lastname: Lu
authors.affiliation: From the Division of Emergency Medicine, Department of Medicine, University of Toronto, Toronto, Ontario, Canada (K.G., C.L.A.); Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada (P.C.A., C.L.A.); University Health Network, Toronto, Ontario, Canada (M.K.K.); and the Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada (P.C.A., M.K.K., H.L., C.L.A.). clare.atzema@ices.on.ca.
authors.forename: Clare L
authors.initials: CL
authors.lastname: Atzema
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging*; D015331:Cohort Studies; D003951:Diagnostic Errors; D004636:Emergency Service, Hospital; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D057216:Propensity Score; D012189:Retrospective Studies; D020521:Stroke / Q000175:diagnosis* / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed; D014717:Vertigo / Q000175:diagnosis* / Q000000981:diagnostic imaging
keywords: computed tomography, x-ray; emergency service, hospital; stroke; vertigo