title: National institutes of health stroke scale item profiles as predictor of patient outcome: external validation on independent trial data.
abstract: OBJECTIVE
  National Institutes of Health Stroke Scale (NIHSS) item profiles that were recently proposed may prove useful both clinically and for research studies. We aimed to validate the NIHSS item profiles in an acute cohort.
  
  
  METHODS
  We conducted a retrospective analysis on pooled data from randomized clinical trials. We applied the latent class analysis probabilities of profile membership developed from the derivation study to obtain symptom grouping, a-NIHSS item profiles. We implemented an independent latent class analysis to derive secondary symptom grouping, b-NIHSS item profiles. Validation was performed by assessing the associations with outcomes and evaluating both sets of NIHSS item profiles' discrimination and calibration to the data. The outcomes evaluated included modified Rankin Scale (mRS; using the full distribution and dichotomized, mRS, 0-1) at day 90 and mortality by 90 days.
  
  
  RESULTS
  We identified 10 271 patients. Ordinal analysis of mRS confirmed increased odds of better outcome across the profiles in a stepwise manner, adjusted for age and thrombolysis treatment, for each set of NIHSS item profiles. Similar patterns were observed for mRS 0 to 1, and inverse patterns were seen for mortality. The c-statistics of a-NIHSS and b-NIHSS item profiles for mRS 0 to 1 were similar at 0.71 (95% confidence interval, 0.70-0.72) and for mortality, 0.74 (0.73-0.75) and 0.75 (0.73-0.76), respectively. Calibration was good.
  
  
  CONCLUSIONS
  These NIHSS item profiles identified using latent class analysis offer a reliable approach to capture the true response patterns that are associated with functional and outcome and mortality post stroke. This approach has the potential to enhance the clinical value of the overall NIHSS score.
authors.affiliation: From the Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (A.H.A.-R., R.L.F., K.R.L.); Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Centre, OH (H.S.); Department of Neurology, University of Cincinnati College of Medicine, OH (D.K., P.K., J.P.B.). Azmil.Abdul-Rahim@glasgow.ac.uk.
authors.forename: Azmil H
authors.initials: AH
authors.lastname: Abdul-Rahim
authors.affiliation: From the Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (A.H.A.-R., R.L.F., K.R.L.); Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Centre, OH (H.S.); Department of Neurology, University of Cincinnati College of Medicine, OH (D.K., P.K., J.P.B.).
authors.forename: Rachael L
authors.initials: RL
authors.lastname: Fulton
authors.affiliation: From the Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (A.H.A.-R., R.L.F., K.R.L.); Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Centre, OH (H.S.); Department of Neurology, University of Cincinnati College of Medicine, OH (D.K., P.K., J.P.B.).
authors.forename: Heidi
authors.initials: H
authors.lastname: Sucharew
authors.affiliation: From the Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (A.H.A.-R., R.L.F., K.R.L.); Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Centre, OH (H.S.); Department of Neurology, University of Cincinnati College of Medicine, OH (D.K., P.K., J.P.B.).
authors.forename: Dawn
authors.initials: D
authors.lastname: Kleindorfer
authors.affiliation: From the Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (A.H.A.-R., R.L.F., K.R.L.); Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Centre, OH (H.S.); Department of Neurology, University of Cincinnati College of Medicine, OH (D.K., P.K., J.P.B.).
authors.forename: Pooja
authors.initials: P
authors.lastname: Khatri
authors.affiliation: From the Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (A.H.A.-R., R.L.F., K.R.L.); Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Centre, OH (H.S.); Department of Neurology, University of Cincinnati College of Medicine, OH (D.K., P.K., J.P.B.).
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Broderick
authors.affiliation: From the Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (A.H.A.-R., R.L.F., K.R.L.); Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Centre, OH (H.S.); Department of Neurology, University of Cincinnati College of Medicine, OH (D.K., P.K., J.P.B.).
authors.forename: Kennedy R
authors.initials: KR
authors.lastname: Lees
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009316:National Institutes of Health (U.S.) / Q000592:standards* / Q000639:trends; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013223:Statistics as Topic / Q000592:standards; D020521:Stroke / Q000175:diagnosis* / Q000401:mortality*; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology
keywords: outcomes research; stroke