title: Comparison of predictive value of activity limitation staging systems based on dichotomous versus trichotomous responses in the Medicare Current Beneficiary Survey.
abstract: BACKGROUND
  Traditional ways of measuring disability include summary indices, binary expressions, or counts of limitations. However, counts of activity of daily living (ADL) or instrumental activity of daily living (IADL) limitations do not specify which activities are limited. Activity limitation staging systems within the ADL and IADL domains depict both the severity and types of limitations experienced and specify clinically meaningful patterns of increasing difficulty with self-care.
  
  
  OBJECTIVE
  To compare the predictive value and utility of ADL and IADL stages based on dichotomous versus trichotomous responses to ADL and IADL questions based on "difficulty" and "receive help" responses.
  
  
  METHODS
  Data were analyzed from the 2005, 2006, and 2007 Medicare Current Beneficiary Survey (MCBS) entry panels on 11,706 beneficiaries. This was a prospective cohort study that examined time to inpatient admission, all-cause mortality, skilled nursing facility (SNF) admission, and long-term care (LTC) facility admission based on dichotomous versus trichotomous stages.
  
  
  RESULTS
  For both ADLs and IADLs, Akaike information criteria for most outcomes were lower (indicating better-performing models) for the trichotomous staging systems than the dichotomous staging systems. The hazard ratios (HRs) and 95% confidence intervals (CIs) of the dichotomous ADL staging system increased as disability increased, whereas the HRs of the other staging systems fluctuated.
  
  
  CONCLUSIONS
  Both staging systems have strong associations with each outcome. The dichotomous staging system is more clinically relevant while the trichotomous staging system may provide utility for clinicians, health care organizations, and policy makers seeking to predict death or admission to a hospital, SNF, or LTC facility.
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA. Electronic address: jkurichi@mailmed.upenn.edu.
authors.forename: Jibby E
authors.initials: JE
authors.lastname: Kurichi
authors.affiliation: Geriatric Psychiatry Section, Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; VISN 4 Mental Illness Research Education and Clinical Center (MIRECC), Philadelphia VA Medical Center, Philadelphia, PA, USA.
authors.forename: Joel E
authors.initials: JE
authors.lastname: Streim
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Hillary R
authors.initials: HR
authors.lastname: Bogner
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Dawei
authors.initials: D
authors.lastname: Xie
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Pui L
authors.initials: PL
authors.lastname: Kwong
authors.affiliation: Center for Clinical Epidemiology and Biostatistics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA; Center for Pharmacoepidemiology Research and Training, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: Sean
authors.initials: S
authors.lastname: Hennessy
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D004185:Disability Evaluation; D006233:Persons with Disabilities; D005260:Female; D006760:Hospitalization; D006801:Humans; D008134:Long-Term Care; D008297:Male; D006278:Medicare; D008875:Middle Aged; D009735:Nursing Homes; D011446:Prospective Studies; D012648:Self Care; D011795:Surveys and Questionnaires; D014481:United States
keywords: Activities of daily living; Disability; Medicare Current Beneficiary Survey; Staging