title: Using a Rasch scale to characterize the clinical features of patients with a clinical diagnosis of uncertain, probable, or possible Alzheimer disease at intake.
abstract: OBJECTIVE
  This study examined the clinical features of patients with clinical diagnoses of probable Alzheimer disease (AD), possible AD, and uncertain.
  
  
  METHODS
  Case study comparing three groups of AD patients diagnosed at their initial visit to an Alzheimer outpatient clinic.
  
  
  METHODS
  Southern Illinois University School of Medicine's Center for Alzheimer Disease and Related Disorders (CADRD) assessment sites (20) in rural Illinois.
  
  
  METHODS
  300 patients assessed at CADRD between January 1, 1994 and July 1, 2000.
  
  
  METHODS
  Patients were given an extensive clinical battery consisting of physical and neurologic examination, mental status testing including the Mini-Mental State Exam (MMSE), Short Blessed Dementia (SBD) and Blessed Dementia Scale (ADL), medical history evaluation, and laboratory tests. Other data included age at visit, gender, and medical history variables.
  
  
  RESULTS
  Mean MMSE, SBD, and ADL scores differed significantly between groups (p's < 0.01). In all three cognitive tests, the uncertain group was the least impaired while the probable AD group was the most impaired. A Rasch model indicated that only the cognitive measures were useful in discriminating between the three diagnostic groups.
  
  
  CONCLUSIONS
  In general, probable AD patients were distinguished from possible AD patients by the severity of their dementia as measured by the MMSE, ADL and SBD as well as Hachinski-Ischemic Score (HIS) scores. A Rasch model did well at predicting group membership based upon dementia measures only. The uncertain group differed from the AD groups in age and dementia severity as measured by the MMSE, ADL and SBD. Noting differences between this and previous studies, we speculate disparity may be related to differences in population ethnicity.
authors.affiliation: Center for Alzheimer Disease and Related Disorders, Southern Illinois University School of Medicine, Springfield 62794-9643, USA. lhughes@siumed.edu
authors.forename: Larry F
authors.initials: LF
authors.lastname: Hughes
authors.forename: Kyle
authors.initials: K
authors.lastname: Perkins
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Wright
authors.forename: Heather
authors.initials: H
authors.lastname: Westrick
mesh_terms: D000203:Activities of Daily Living / Q000145:classification*; D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000175:diagnosis* / Q000453:epidemiology; D015897:Comorbidity; D005260:Female; D015577:Geriatric Assessment / Q000706:statistics & numerical data*; D006801:Humans; D007087:Illinois; D008297:Male; D008609:Mental Status Schedule / Q000706:statistics & numerical data*; D008875:Middle Aged; D009460:Neurologic Examination / Q000706:statistics & numerical data; D009483:Neuropsychological Tests / Q000706:statistics & numerical data*; D011336:Probability; D011594:Psychometrics / Q000706:statistics & numerical data