title: Putting the Alzheimer's cognitive test to the test I: traditional psychometric methods.
abstract: BACKGROUND
  The Alzheimer's Disease Assessment Scale-Cognitive Behavior section (ADAS-Cog) is the most commonly used cognitive test in AD clinical trials. However, there are concerns about its use in early-stage disease. Herein we examine those concerns using traditional psychometric methods.
  
  
  METHODS
  We analyzed ADAS-Cog data (n = 675) based on six psychometric properties: data completeness; scaling assumptions; targeting; reliability; validity; and responsiveness.
  
  
  RESULTS
  At the scale-level, criteria tested for data completeness, scaling assumptions (item total correlations 0.33-0.59), targeting (no floor/ceiling effects), reliability (Cronbach's α = 0.74), and validity (correlation with MMSE = -0.70) were satisfied. Responsiveness (baseline to 12 months; n = 145) was moderate to high (effect size = -0.73). However, 8 of 11 ADAS-Cog components had substantial ceiling effects (range 32%-83%), and decreased responsiveness associated with low to moderate effect sizes (0.14-0.65).
  
  
  CONCLUSIONS
  In our study, many patients with AD found large portions of the ADAS-Cog too easy. Future research should consider modifying the ADAS-Cog or developing a new test.
authors.affiliation: Clinical Neurology Research Group, Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, UK. Jeremy.Hobart@pms.ac.uk
authors.forename: Jeremy
authors.initials: J
authors.lastname: Hobart
authors.forename: Stefan
authors.initials: S
authors.lastname: Cano
authors.forename: Holly
authors.initials: H
authors.lastname: Posner
authors.forename: Ola
authors.initials: O
authors.lastname: Selnes
authors.forename: Yaakov
authors.initials: Y
authors.lastname: Stern
authors.forename: Ronald
authors.initials: R
authors.lastname: Thomas
authors.forename: John
authors.initials: J
authors.lastname: Zajicek
mesh_terms: D000544:Alzheimer Disease / Q000175:diagnosis* / Q000523:psychology; D006801:Humans; D009483:Neuropsychological Tests; D011594:Psychometrics / Q000379:methods*; D015203:Reproducibility of Results