title: Subarachnoid hemorrhage admissions retrospectively identified using a prediction model.
abstract: OBJECTIVE
  To create an accurate prediction model using variables collected in widely available health administrative data records to identify hospitalizations for primary subarachnoid hemorrhage (SAH).
  
  
  METHODS
  A previously established complete cohort of consecutive primary SAH patients was combined with a random sample of control hospitalizations. Chi-square recursive partitioning was used to derive and internally validate a model to predict the probability that a patient had primary SAH (due to aneurysm or arteriovenous malformation) using health administrative data.
  
  
  RESULTS
  A total of 10,322 hospitalizations with 631 having primary SAH (6.1%) were included in the study (5,122 derivation, 5,200 validation). In the validation patients, our recursive partitioning algorithm had a sensitivity of 96.5% (95% confidence interval [CI] 93.9-98.0), a specificity of 99.8% (95% CI 99.6-99.9), and a positive likelihood ratio of 483 (95% CI 254-879). In this population, patients meeting criteria for the algorithm had a probability of 45% of truly having primary SAH.
  
  
  CONCLUSIONS
  Routinely collected health administrative data can be used to accurately identify hospitalized patients with a high probability of having a primary SAH. This algorithm may allow, upon validation, an easy and accurate method to create validated cohorts of primary SAH from either ruptured aneurysm or arteriovenous malformation.
authors.affiliation: From the Department of Medicine (Critical Care) (S.W.E., L.M.), Clinical Epidemiology Program (S.W.E, L.M., D.F., A.F., C.v.W.), Ottawa Hospital Research Institute/The Ottawa Hospital; Department of Anesthesia (Critical Care) (A.T., M.C.), Hôpital de L'Enfant-Jésus, Quebec; and Departments of Medical Imaging (M.P.d.S., C.L.), Surgery (Neuro-Surgery) (J.S.), and Medicine (C.v.W, A.F.), The Ottawa Hospital, Canada. senglish@ohri.ca.
authors.forename: Shane W
authors.initials: SW
authors.lastname: English
authors.affiliation: From the Department of Medicine (Critical Care) (S.W.E., L.M.), Clinical Epidemiology Program (S.W.E, L.M., D.F., A.F., C.v.W.), Ottawa Hospital Research Institute/The Ottawa Hospital; Department of Anesthesia (Critical Care) (A.T., M.C.), Hôpital de L'Enfant-Jésus, Quebec; and Departments of Medical Imaging (M.P.d.S., C.L.), Surgery (Neuro-Surgery) (J.S.), and Medicine (C.v.W, A.F.), The Ottawa Hospital, Canada.
authors.forename: Lauralyn
authors.initials: L
authors.lastname: McIntyre
authors.affiliation: From the Department of Medicine (Critical Care) (S.W.E., L.M.), Clinical Epidemiology Program (S.W.E, L.M., D.F., A.F., C.v.W.), Ottawa Hospital Research Institute/The Ottawa Hospital; Department of Anesthesia (Critical Care) (A.T., M.C.), Hôpital de L'Enfant-Jésus, Quebec; and Departments of Medical Imaging (M.P.d.S., C.L.), Surgery (Neuro-Surgery) (J.S.), and Medicine (C.v.W, A.F.), The Ottawa Hospital, Canada.
authors.forename: Dean
authors.initials: D
authors.lastname: Fergusson
authors.affiliation: From the Department of Medicine (Critical Care) (S.W.E., L.M.), Clinical Epidemiology Program (S.W.E, L.M., D.F., A.F., C.v.W.), Ottawa Hospital Research Institute/The Ottawa Hospital; Department of Anesthesia (Critical Care) (A.T., M.C.), Hôpital de L'Enfant-Jésus, Quebec; and Departments of Medical Imaging (M.P.d.S., C.L.), Surgery (Neuro-Surgery) (J.S.), and Medicine (C.v.W, A.F.), The Ottawa Hospital, Canada.
authors.forename: Alexis
authors.initials: A
authors.lastname: Turgeon
authors.affiliation: From the Department of Medicine (Critical Care) (S.W.E., L.M.), Clinical Epidemiology Program (S.W.E, L.M., D.F., A.F., C.v.W.), Ottawa Hospital Research Institute/The Ottawa Hospital; Department of Anesthesia (Critical Care) (A.T., M.C.), Hôpital de L'Enfant-Jésus, Quebec; and Departments of Medical Imaging (M.P.d.S., C.L.), Surgery (Neuro-Surgery) (J.S.), and Medicine (C.v.W, A.F.), The Ottawa Hospital, Canada.
authors.forename: Marlise P
authors.initials: MP
authors.lastname: Dos Santos
authors.affiliation: From the Department of Medicine (Critical Care) (S.W.E., L.M.), Clinical Epidemiology Program (S.W.E, L.M., D.F., A.F., C.v.W.), Ottawa Hospital Research Institute/The Ottawa Hospital; Department of Anesthesia (Critical Care) (A.T., M.C.), Hôpital de L'Enfant-Jésus, Quebec; and Departments of Medical Imaging (M.P.d.S., C.L.), Surgery (Neuro-Surgery) (J.S.), and Medicine (C.v.W, A.F.), The Ottawa Hospital, Canada.
authors.forename: Cheemun
authors.initials: C
authors.lastname: Lum
authors.affiliation: From the Department of Medicine (Critical Care) (S.W.E., L.M.), Clinical Epidemiology Program (S.W.E, L.M., D.F., A.F., C.v.W.), Ottawa Hospital Research Institute/The Ottawa Hospital; Department of Anesthesia (Critical Care) (A.T., M.C.), Hôpital de L'Enfant-Jésus, Quebec; and Departments of Medical Imaging (M.P.d.S., C.L.), Surgery (Neuro-Surgery) (J.S.), and Medicine (C.v.W, A.F.), The Ottawa Hospital, Canada.
authors.forename: Michaël
authors.initials: M
authors.lastname: Chassé
authors.affiliation: From the Department of Medicine (Critical Care) (S.W.E., L.M.), Clinical Epidemiology Program (S.W.E, L.M., D.F., A.F., C.v.W.), Ottawa Hospital Research Institute/The Ottawa Hospital; Department of Anesthesia (Critical Care) (A.T., M.C.), Hôpital de L'Enfant-Jésus, Quebec; and Departments of Medical Imaging (M.P.d.S., C.L.), Surgery (Neuro-Surgery) (J.S.), and Medicine (C.v.W, A.F.), The Ottawa Hospital, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Sinclair
authors.affiliation: From the Department of Medicine (Critical Care) (S.W.E., L.M.), Clinical Epidemiology Program (S.W.E, L.M., D.F., A.F., C.v.W.), Ottawa Hospital Research Institute/The Ottawa Hospital; Department of Anesthesia (Critical Care) (A.T., M.C.), Hôpital de L'Enfant-Jésus, Quebec; and Departments of Medical Imaging (M.P.d.S., C.L.), Surgery (Neuro-Surgery) (J.S.), and Medicine (C.v.W, A.F.), The Ottawa Hospital, Canada.
authors.forename: Alan
authors.initials: A
authors.lastname: Forster
authors.affiliation: From the Department of Medicine (Critical Care) (S.W.E., L.M.), Clinical Epidemiology Program (S.W.E, L.M., D.F., A.F., C.v.W.), Ottawa Hospital Research Institute/The Ottawa Hospital; Department of Anesthesia (Critical Care) (A.T., M.C.), Hôpital de L'Enfant-Jésus, Quebec; and Departments of Medical Imaging (M.P.d.S., C.L.), Surgery (Neuro-Surgery) (J.S.), and Medicine (C.v.W, A.F.), The Ottawa Hospital, Canada.
authors.forename: Carl
authors.initials: C
authors.lastname: van Walraven
mesh_terms: D000046:Academic Medical Centers; D059019:Clinical Coding; D015331:Cohort Studies; D016208:Databases, Factual; D006801:Humans; D016015:Logistic Models; D008491:Medical Informatics Applications; D008962:Models, Theoretical; D015999:Multivariate Analysis; D010343:Patient Admission; D015995:Prevalence; D011336:Probability; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis* / Q000628:therapy*; D062606:Tertiary Care Centers