title: Diagnostic test utilization in the emergency department for alert headache patients with possible subarachnoid hemorrhage.
abstract: OBJECTIVE
  This study evaluated the incidence of subarachnoid hemorrhage (SAH) and the use of computed tomography (CT) and lumbar puncture (LP) in a cohort of emergency department (ED) patients with acute headache.
  
  
  METHODS
  Health records from a tertiary care ED were used to identify all patients over 15 years of age who presented with headache over a 10-month period. Patients were excluded if they had been referred with confirmed SAH or if they had recurrent headache, head trauma, decreased level of consciousness or new neurologic deficits. Outcome measures included ED diagnosis, use of CT or LP, and ED length of stay. Analysis included descriptive statistics, 95% confidence intervals (CIs) and analysis of variance for length of stay.
  
  
  RESULTS
  The mean age of the 891 patients was 41.9 years. Ten (1.1%) of the patients had SAH, 313 (35.1%) underwent CT, and 85 (9.5%) underwent LP. Only 9 (2.9%) of the CT scans and 2 (2.4%) of the LPs were positive for SAH. Of the 296 patients with normal CT results, 232 (78.4%) did not undergo subsequent LP. The mean length of stay was 4.0 hours (95% CI, 3.8-4.1) if no diagnostic testing was performed, 5.0 hours (95% CI, 4.7-5.4) if CT was performed and 7.1 hours (95% CI, 6.3-7.9) if LP was performed (p = 0.001).
  
  
  CONCLUSIONS
  Diagnostic testing was associated with substantially prolonged lengths of stay. CT and LP had low diagnostic yields, which suggests the need for a clinical decision rule to rule out SAH in ED patients with acute headache.
authors.affiliation: Division of Emergency Medicine, Department of Epidemiology and Community Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Perry
authors.forename: Ian
authors.initials: I
authors.lastname: Stiell
authors.forename: George
authors.initials: G
authors.lastname: Wells
authors.forename: Alena
authors.initials: A
authors.lastname: Spacek