title: LP or not LP, that is the question: gold standard or unnecessary procedure in subarachnoid haemorrhage?
abstract: OBJECTIVE
  To measure the sensitivity of modern CT in patients presenting to the emergency department and evaluated for possible subarachnoid haemorrhage, with particular attention to those presenting within 12 h of ictus.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  Large district general hospital emergency department seeing 73,500 new attendances per year.
  
  
  METHODS
  Patients presenting to the emergency department and screened for suspected subarachnoid haemorrhage.
  
  
  METHODS
  Subarachnoid haemorrhage was defined by either the presence of subarachnoid blood on CT, positive CSF spectrophotometry defined by national guidelines or aneurysm identified on subsequent angiography if either of the former were equivocal.
  
  
  RESULTS
  244 patients were screened for subarachnoid haemorrhage during the 24 months between March 2006 and April 2008 (mean age 48.5 years). The sensitivity of CT overall for subarachnoid haemorrhage was 93.8% (95% CI 84% to 98%) increasing to 95% (95% CI 82% to 99%) if performed within 12 h of ictus.
  
  
  CONCLUSIONS
  While modern CT has a high sensitivity for the diagnosis of acute subarachnoid haemorrhage, particularly within 12 h of ictus, it is still not sufficient to act as the sole diagnostic tool, and patients with a negative CT will require further investigation with a lumbar puncture.
authors.affiliation: Emergency Department, Torbay Hospital, Torquay, Devon, UK.
authors.forename: Hannah
authors.identifier: http://orcid.org/0000-0001-5722-9664
authors.initials: H
authors.lastname: Stewart
authors.affiliation: Emergency Department, Royal Devon and Exeter Hospital, Exeter, UK.
authors.forename: Adam
authors.initials: A
authors.lastname: Reuben
authors.affiliation: Emergency Department, Royal Devon and Exeter Hospital, Exeter, UK.
authors.forename: James
authors.initials: J
authors.lastname: McDonald
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013129:Spinal Puncture; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis*; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000592:standards*; D006113:United Kingdom; D019564:Unnecessary Procedures; D055815:Young Adult
keywords: acute medicine-other; admission aviodance; assessment; imaging, CT/MRI; neurology, headache