title: Validity of the NIHSS in predicting arterial occlusion in cerebral infarction is time-dependent.
abstract: BACKGROUND
  The NIH Stroke Scale (NIHSS) is used to assess acute ischemic stroke severity and outcome. High NIHSS scores are usually associated with arterial occlusion but it is unknown what the effect of time to clinical evaluation (TTCE) in this association is. We tested the NIHSS scores as an instrument to determine vessel occlusion (VO) at different time points from symptom onset.
  
  
  METHODS
  Patients were selected from our prospective stroke database if they had admission NIHSS scores and intracranial vessel neuroimaging studies. We dichotomized patients according to VO and TTCE. Receiver operating curves, c statistics, and odds ratios were calculated to study the validity of the NIHSS score.
  
  
  RESULTS
  Among 463 patients (mean age 70.2 years, 53.1% male, median NIHSS 4, median TTCE 3.3 hours), 22.5% had arterial occlusion. Median NIHSS scores were higher in patients with VO, 10.5 (interquartile range 5-18) vs 3 (2-7), p<0.001, and in those with TTCE<6 hours, 15 (interquartile range 7-19) vs 4 (2-8) if ≥6 hours, p<0.001. Receiver operating characteristic curves showed that the validity of NIHSS in predicting VO was higher in patients with TTCE<6 hours, p=0.03. The best cutoff point in patients evaluated before 6 hours was an NIHSS of 7 (76.2% sensitivity, specificity 70.1%), while in patients evaluated after 6 hours the best cutoff point was 4 (sensitivity 65.4%, specificity 62.0%).
  
  
  CONCLUSIONS
  Our study shows that the validity of NIHSS scores in predicting arterial occlusion is time-dependent, decreasing with increasing time from symptom onset to clinical evaluation.
authors.affiliation: Epidemiology and Public Health Policy Center, Department of Academic and Scientific Development, Clínica Alemana de Santiago, Facultad de Medicina, Universidad del Desarrollo, Avenida Vitacura 5951, Vitacura, 7650568, Santiago, Chile. veroolavarria@yahoo.com
authors.forename: V V
authors.initials: VV
authors.lastname: Olavarría
authors.forename: I
authors.initials: I
authors.lastname: Delgado
authors.forename: A
authors.initials: A
authors.lastname: Hoppe
authors.forename: A
authors.initials: A
authors.lastname: Brunser
authors.forename: D
authors.initials: D
authors.lastname: Cárcamo
authors.forename: V
authors.initials: V
authors.lastname: Díaz-Tapia
authors.forename: P M
authors.initials: PM
authors.lastname: Lavados
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001157:Arterial Occlusive Diseases / Q000175:diagnosis* / Q000209:etiology*; D001921:Brain / Q000000981:diagnostic imaging / Q000473:pathology; D002544:Cerebral Infarction / Q000150:complications*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D005260:Female; D006801:Humans; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D009316:National Institutes of Health (U.S.); D009460:Neurologic Examination; D011237:Predictive Value of Tests; D012372:ROC Curve; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D013997:Time Factors; D015898:Tomography Scanners, X-Ray Computed; D017585:Ultrasonography, Doppler, Transcranial; D014481:United States