title: Assessing the suitability of sets-based approaches: estimating the discriminative power of risk models for ordinal outcome treatments.
abstract: In order to evaluate the discrimination performance of an ordinal model for improved disease screening, a new test was proposed where information was obtained across all samples simultaneously.
  
  
  
  The ordinal c-index builds upon the volume under the surface methodology without focusing on the accompanying receiver operating characteristic surfaces. However, it can be simplified to an average of pairwise c-indexes. In this paper, a set-based estimate (information was obtained across all samples simultaneously) was proposed by summing all correctly ordered groups. The asymptotic distribution of this proposed estimate was derived using U-statistics.
  
  
  
  A predictive model was applied using the blood urea nitrogen/creatinine ratio to discriminate stroke in evolution in acute ischemic stroke patients, which could potentially be life-saving in emergency departments.
  
  
  
  By conducting Monte Carlo simulations, it was concluded that the measure proposed herein is a better choice for clinical use because of the asymmetry of the predicted probabilities of groups.
authors.affiliation: College of Nursing & the Chronic Diseases and Health Promotion Research Center, Chang Gung University of Science and Technology, Chiayi Campus, Chiayi, Taiwan howellchang@gmail.com.|Department of Nursing, Chang Gung University of Science and Technology, Chiayi Campus, Chiayi, Taiwan.
authors.forename: Chia-Hao
authors.initials: CH
authors.lastname: Chang
authors.affiliation: Department of Nursing, Chang Gung University of Science and Technology, Chiayi Campus, Chiayi, Taiwan.|Department of Emergency Medicine, Chang Gung Memorial Hospital, Chiayi, Taiwan.
authors.forename: Leng-Chieh
authors.initials: LC
authors.lastname: Lin
authors.affiliation: Department of Nursing, Chang Gung University of Science and Technology, Chiayi Campus, Chiayi, Taiwan.|Department of Emergency Medicine, Chang Gung Memorial Hospital, Chiayi, Taiwan.
authors.forename: I-Chuan
authors.initials: IC
authors.lastname: Chen
authors.affiliation: Department of Industrial Engineering & Management Information, Huafan University, New Taipei City, Taiwan.
authors.forename: Ching-Ho
authors.initials: CH
authors.lastname: Yen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009010:Monte Carlo Method; D012372:ROC Curve; D018570:Risk Assessment / Q000379:methods* / Q000706:statistics & numerical data*; D020521:Stroke / Q000175:diagnosis*
keywords: Acute ischemic stroke; Discriminative power; National institutes of health stroke scale; Ordinal outcomes; Stroke in evolution