title: Differentiation between traumatic tap and aneurysmal subarachnoid hemorrhage: prospective cohort study.
abstract: OBJECTIVE
  To describe the findings in cerebrospinal fluid from patients with acute headache that could distinguish subarachnoid hemorrhage from the effects of a traumatic lumbar puncture.
  
  
  METHODS
  A substudy of a prospective multicenter cohort study.
  
  
  METHODS
  12 Canadian academic emergency departments, from November 2000 to December 2009.
  
  
  METHODS
  Alert patients aged over 15 with an acute non-traumatic headache who underwent lumbar puncture to rule out subarachnoid hemorrhage.
  
  
  METHODS
  Aneurysmal subarachnoid hemorrhage requiring intervention or resulting in death.
  
  
  RESULTS
  Of the 1739 patients enrolled, 641 (36.9%) had abnormal results on cerebrospinal fluid analysis with >1 × 10(6)/L red blood cells in the final tube of cerebrospinal fluid and/or xanthochromia in one or more tubes. There were 15 (0.9%) patients with aneurysmal subarachnoid hemorrhage based on abnormal results of a lumbar puncture. The presence of fewer than 2000 × 10(6)/L red blood cells in addition to no xanthochromia excluded the diagnosis of aneurysmal subarachnoid hemorrhage, with a sensitivity of 100% (95% confidence interval 74.7% to 100%) and specificity of 91.2% (88.6% to 93.3%).
  
  
  CONCLUSIONS
  No xanthochromia and red blood cell count <2000 × 10(6)/L reasonably excludes the diagnosis of aneurysmal subarachnoid hemorrhage. Most patients with acute headache who meet this cut off will need no further investigations and aneurysmal subarachnoid hemorrhage can be excluded as a cause of their headache.
authors.affiliation: Department of Emergency Medicine, University of Ottawa, Ottawa Hospital Research Institute, Ottawa Hospital 1053 Carling Avenue Room F647, Ottawa, ON, Canada, K1Y 4E9 jperry@ohri.ca.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Perry
authors.affiliation: Department of Emergency Medicine, University of Ottawa, Ottawa Hospital Research Institute, Ottawa Hospital 1053 Carling Avenue Room F647, Ottawa, ON, Canada, K1Y 4E9.
authors.forename: Bader
authors.initials: B
authors.lastname: Alyahya
authors.affiliation: University of Ottawa, Department of Emergency Medicine, Ottawa, ON, Canada.
authors.forename: Marco L A
authors.initials: ML
authors.lastname: Sivilotti
authors.affiliation: Department of Emergency Medicine, University of Alberta, Edmonton, AB, Canada.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bullard
authors.affiliation: Hopital de l'Enfant-Jesus, Department of Emergency Medicine, Faculty of Medicine, Quebec City, QC, Canada G1J 1Z4.
authors.forename: Marcel
authors.initials: M
authors.lastname: Émond
authors.affiliation: Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, ON, Canada.
authors.forename: Jane
authors.initials: J
authors.lastname: Sutherland
authors.affiliation: Department of Emergency Medicine, McMaster University, Hamilton, ON, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Worster
authors.affiliation: Department of Emergency Medicine, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Corinne
authors.initials: C
authors.lastname: Hohl
authors.affiliation: Division of Emergency Medicine, University of Toronto, Toronto, ON, Canada.
authors.forename: Jacques S
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Division of Emergency Medicine, University of Western Ontario, London, ON, Canada.
authors.forename: Mary A
authors.initials: MA
authors.lastname: Eisenhauer
authors.affiliation: Department of Emergency Medicine, University of Manitoba, Winnipeg, MB, Canada.
authors.forename: Merril
authors.initials: M
authors.lastname: Pauls
authors.affiliation: Division of Neurosurgery, University of Ottawa, Ottawa, ON, Canada.
authors.forename: Howard
authors.initials: H
authors.lastname: Lesiuk
authors.affiliation: Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa Hospital Research Institute, Ottawa, ON, Canada.
authors.forename: George A
authors.initials: GA
authors.lastname: Wells
authors.affiliation: Department of Emergency Medicine, University of Ottawa, Ottawa Hospital Research Institute, Ottawa Hospital 1053 Carling Avenue Room F647, Ottawa, ON, Canada, K1Y 4E9.
authors.forename: Ian G
authors.initials: IG
authors.lastname: Stiell
mesh_terms: D000328:Adult; D002170:Canada; D003937:Diagnosis, Differential; D003952:Diagnostic Imaging; D004906:Erythrocyte Count; D005260:Female; D006261:Headache / Q000134:cerebrospinal fluid; D006801:Humans; D002532:Intracranial Aneurysm / Q000134:cerebrospinal fluid*; D008297:Male; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013129:Spinal Puncture / Q000009:adverse effects*; D013345:Subarachnoid Hemorrhage / Q000134:cerebrospinal fluid*