title: Reliability and Validity of the Clinical Dementia Rating for Community-Living Elderly Subjects without an Informant.
abstract: BACKGROUND
  The Clinical Dementia Rating (CDR) scale is widely used to assess cognitive impairment in Alzheimer's disease. It requires collateral information from a reliable informant who is not available in many instances. We adapted the original CDR scale for use with elderly subjects without an informant (CDR-NI) and evaluated its reliability and validity for assessing mild cognitive impairment (MCI) and dementia among community-dwelling elderly subjects.
  
  
  METHODS
  At two consecutive visits 1 week apart, nurses trained in CDR assessment interviewed, observed and rated cognitive and functional performance according to a protocol in 90 elderly subjects with suboptimal cognitive performance [Mini-Mental State Examination (MMSE) <26 and/or Montreal Cognitive Assessment (MOCA) <26] and without informants according to a protocol. CDR domains and global scores were assigned after the second visit based upon corroborative information from the subjects' responses to questions, role-play, and observed performance in specifically assigned tasks at home and within the community.
  
  
  RESULTS
  The CDR-NI scores (0, 0.5, 1) showed good internal consistency (Crohnbach's α 0.83-0.84), inter-rater reliability (κ 0.77-1.00 for six domains and 0.95 for global rating) and test-retest reliability (κ 0.75-1.00 for six domains and 0.80 for global rating), good agreement (κ 0.79) with the clinical assessment status of MCI (n = 37) and dementia (n = 4) and significant differences in the mean scores for MMSE, MOCA and Instrumental Activities of Daily Living (ANOVA global p < 0.001).
  
  
  CONCLUSIONS
  Owing to the protocol of the interviews, assessments and structured observations gathered during the two visits, CDR-NI provides valid and reliable assessment of MCI and dementia in community-living elderly subjects without an informant.
authors.affiliation: Gerontology Research Programme, Yong Loo Lin School of Medicine, Singapore ; Department of Psychological Medicine, Yong Loo Lin School of Medicine, Singapore.
authors.forename: Ma Shwe Zin
authors.initials: MS
authors.lastname: Nyunt
authors.affiliation: Department of Geriatric Medicine, Tan Tock Seng Hospital, National University of Singapore, Singapore.
authors.forename: Mei Sian
authors.initials: MS
authors.lastname: Chong
authors.affiliation: Department of Geriatric Medicine, Tan Tock Seng Hospital, National University of Singapore, Singapore.
authors.forename: Wee Shiong
authors.initials: WS
authors.lastname: Lim
authors.affiliation: Neuroscience Program, Duke-NUS Graduate Medical School, Singapore.
authors.forename: Tih Shih
authors.initials: TS
authors.lastname: Lee
authors.affiliation: Department of Geriatric Medicine, Khoo Teck Puat Hospital, Singapore, Singapore.
authors.forename: Philip
authors.initials: P
authors.lastname: Yap
authors.affiliation: Gerontology Research Programme, Yong Loo Lin School of Medicine, Singapore ; Department of Psychological Medicine, Yong Loo Lin School of Medicine, Singapore.
authors.forename: Tze Pin
authors.initials: TP
authors.lastname: Ng
keywords: Alzheimer's disease; Clinical Dementia Rating; Community-living elderly subjects; Mild cognitive impairment; Mini-Mental State Examination; Neuropsychological tests