title: Greater precision when measuring dementia severity: establishing item parameters for the Clinical Dementia Rating Scale.
abstract: OBJECTIVE
  An item response theory (IRT)-based scoring approach to the Clinical Dementia Rating Scale (CDR) can account for the pattern of scores across the CDR items (domains) and their differential abilities to indicate dementia severity. In doing so, an IRT-based approach can provide greater precision than other CDR scoring algorithms. However, neither a good set of item parameters nor an easily digestible set of instructions needed to implement this approach is readily available.
  
  
  METHODS
  Participants were 1,326 patients at the Baylor College of Medicine Alzheimer's Disease and Memory Disorders Clinic.
  
  
  RESULTS
  The item parameters necessary for an IRT-based scoring approach were identified (a parameters ranged from 3.01 to 6.22; b parameters ranged from -2.46 to 2.07).
  
  
  CONCLUSIONS
  This study provides, and demonstrates how to easily apply, IRT-based item parameters for the CDR
authors.affiliation: Department of Psychology, Texas A & M University, 4235 TAMU, College Station, TX 77843, USA. dalowe@tamu.edu
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Lowe
authors.forename: Steve
authors.initials: S
authors.lastname: Balsis
authors.forename: Tyler M
authors.initials: TM
authors.lastname: Miller
authors.forename: Jared F
authors.initials: JF
authors.lastname: Benge
authors.forename: Rachelle S
authors.initials: RS
authors.lastname: Doody
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D000544:Alzheimer Disease / Q000145:classification / Q000175:diagnosis*; D003704:Dementia / Q000145:classification / Q000175:diagnosis*; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D016013:Likelihood Functions; D008297:Male; D009483:Neuropsychological Tests / Q000706:statistics & numerical data*; D012720:Severity of Illness Index