title: Sensitivity of Early Brain Computed Tomography to Exclude Aneurysmal Subarachnoid Hemorrhage: A Systematic Review and Meta-Analysis.
abstract: OBJECTIVE
  Emerging evidence demonstrating the high sensitivity of early brain computed tomography (CT) brings into question the necessity of always performing lumbar puncture after a negative CT in the diagnosis of spontaneous subarachnoid hemorrhage (SAH). Our objective was to determine the sensitivity of brain CT using modern scanners (16-slice technology or greater) when performed within 6 hours of headache onset to exclude SAH in neurologically intact patients.
  
  
  METHODS
  After conducting a comprehensive literature search using Ovid MEDLINE, Ovid EMBASE, Web of Science, and Scopus, we conducted a meta-analysis. We included original research studies of adults presenting with a history concerning for spontaneous SAH and who had noncontrast brain CT scan using a modern generation multidetector CT scanner within 6 hours of symptom onset. Our study adheres to the preferred reporting items for systematic reviews and meta-analyses (PRISMA).
  
  
  RESULTS
  A total of 882 titles were reviewed and 5 articles met inclusion criteria, including an estimated 8907 patients. Thirteen had a missed SAH (incidence 1.46 per 1000) on brain CTs within 6 hours. Overall sensitivity of the CT was 0.987 (95% confidence intervals, 0.971-0.994) and specificity was 0.999 (95% confidence intervals, 0.993-1.0). The pooled likelihood ratio of a negative CT was 0.010 (95% confidence intervals, 0.003-0.034).
  
  
  CONCLUSIONS
  In patients presenting with thunderclap headache and normal neurological examination, normal brain CT within 6 hours of headache is extremely sensitive in ruling out aneurysmal SAH.
authors.affiliation: From the Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA (N.M.D., J.A.E.); Department of Emergency Medicine, Harvard Medical School, Boston, MA (N.M.D., J.A.E.); Departments of Emergency Medicine (M.F.B.) and Neurology (A.A.R.), Mayo Clinic, Rochester, MN. ndubosh@bidmc.harvard.edu.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Dubosh
authors.affiliation: From the Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA (N.M.D., J.A.E.); Department of Emergency Medicine, Harvard Medical School, Boston, MA (N.M.D., J.A.E.); Departments of Emergency Medicine (M.F.B.) and Neurology (A.A.R.), Mayo Clinic, Rochester, MN.
authors.forename: M Fernanda
authors.initials: MF
authors.lastname: Bellolio
authors.affiliation: From the Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA (N.M.D., J.A.E.); Department of Emergency Medicine, Harvard Medical School, Boston, MA (N.M.D., J.A.E.); Departments of Emergency Medicine (M.F.B.) and Neurology (A.A.R.), Mayo Clinic, Rochester, MN.
authors.forename: Alejandro A
authors.initials: AA
authors.lastname: Rabinstein
authors.affiliation: From the Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA (N.M.D., J.A.E.); Department of Emergency Medicine, Harvard Medical School, Boston, MA (N.M.D., J.A.E.); Departments of Emergency Medicine (M.F.B.) and Neurology (A.A.R.), Mayo Clinic, Rochester, MN.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Edlow
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging*; D016022:Case-Control Studies; D015331:Cohort Studies; D051270:Headache Disorders, Primary / Q000000981:diagnostic imaging / Q000209:etiology; D006801:Humans; D013345:Subarachnoid Hemorrhage / Q000150:complications / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000592:standards*
keywords: brain; cerebrospinal fluid; confidence intervals; headache; subarachnoid hemorrhage