title: Validation of cerebrospinal fluid findings in aneurysmal subarachnoid hemorrhage.
abstract: BACKGROUND
  Recently proposed cutoff criteria for cerebrospinal fluid (CSF) analyses might safely exclude a diagnosis of aneurysmal subarachnoid hemorrhage (aSAH).
  
  
  OBJECTIVE
  The objective of this study was to examine the sensitivity of a CSF red blood cell (RBC) count greater than 2000 × 10(6)/L (ie, 2000 RBCs per microliter) or the presence of visible CSF xanthochromia in identifying patients with aSAH.
  
  
  METHODS
  We identified a retrospective case series of patients diagnosed with aSAH after lumbar puncture (LP) in an integrated health delivery system between January 2000 and June 2013 by chart review. All identified patients had at least 1 cerebral aneurysm that was treated with a neurosurgical or endovascular intervention during the index hospitalization. The lowest CSF RBC count was used for validation analysis. Cerebrospinal fluid color was determined by visual inspection. Xanthochromia was defined as pink, orange, or yellow pigmentation of CSF supernatant.
  
  
  RESULTS
  Sixty-four patients met study inclusion criteria. Of these, 17 (33%) of 52 underwent LP within 12 hours of headache onset, and 49 (84%) of 58 exhibited CSF xanthochromia. The median CSF RBC count was 63250 × 10(6)/L. The sensitivity of a CSF RBC count of greater than 2000 × 10(6)/L in identifying aSAH was 96.9% (95% confidence interval, 89.3%-99.1%). Additional consideration of CSF xanthochromia resulted in a sensitivity of 100% (95% confidence interval, 94.3%-100%).
  
  
  CONCLUSIONS
  All patients in this case series of patients with aSAH had either a CSF RBC count greater than 2000 × 10(6)/L or visible CSF xanthochromia, increasing the likelihood that this proposed cutoff strategy may safely identify patients who warrant further investigation for an aneurysmal cause of subarachnoid hemorrhage.
authors.affiliation: Department of Emergency Medicine, Kaiser Permanente, Oakland, CA.
authors.forename: Dustin G
authors.initials: DG
authors.lastname: Mark
authors.affiliation: Department of Emergency Medicine, Kaiser Permanente, San Leandro, CA.
authors.forename: Mamata V
authors.initials: MV
authors.lastname: Kene
authors.affiliation: Department of Emergency Medicine, Kaiser Permanente, South Sacramento, CA.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Offerman
authors.affiliation: Department of Emergency Medicine, Kaiser Permanente, Roseville, CA; Kaiser Permanente Division of Research, Oakland, CA.
authors.forename: David R
authors.initials: DR
authors.lastname: Vinson
authors.affiliation: Kaiser Permanente Division of Research, Oakland, CA; Department of Emergency Medicine, Kaiser Permanente, San Rafael, CA.
authors.forename: Dustin W
authors.initials: DW
authors.lastname: Ballard
mesh_terms: D000368:Aged; D015331:Cohort Studies; D004636:Emergency Service, Hospital; D004906:Erythrocyte Count; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000134:cerebrospinal fluid* / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D013129:Spinal Puncture; D013345:Subarachnoid Hemorrhage / Q000134:cerebrospinal fluid* / Q000175:diagnosis*