title: Measuring the quality of life in mild to very severe dementia: testing the inter-rater and intra-rater reliability of the German version of the QUALIDEM.
abstract: BACKGROUND
  Quality of life (Qol) is an increasingly used outcome measure in dementia research. The QUALIDEM is a dementia-specific and proxy-rated Qol instrument. We aimed to determine the inter-rater and intra-rater reliability in residents with dementia in German nursing homes.
  
  
  METHODS
  The QUALIDEM consists of nine subscales that were applied to a sample of 108 people with mild to severe dementia and six consecutive subscales that were applied to a sample of 53 people with very severe dementia. The proxy raters were 49 registered nurses and nursing assistants. Inter-rater and intra-rater reliability scores were calculated on the subscale and item level.
  
  
  RESULTS
  None of the QUALIDEM subscales showed strong inter-rater reliability based on the single-measure Intra-Class Correlation Coefficient (ICC) for absolute agreement ≥ 0.70. Based on the average-measure ICC for four raters, eight subscales for people with mild to severe dementia (care relationship, positive affect, negative affect, restless tense behavior, social relations, social isolation, feeling at home and having something to do) and five subscales for very severe dementia (care relationship, negative affect, restless tense behavior, social relations and social isolation) yielded a strong inter-rater agreement (ICC: 0.72-0.86). All of the QUALIDEM subscales, regardless of dementia severity, showed strong intra-rater agreement. The ICC values ranged between 0.70 and 0.79 for people with mild to severe dementia and between 0.75 and 0.87 for people with very severe dementia.
  
  
  CONCLUSIONS
  This study demonstrated insufficient inter-rater reliability and sufficient intra-rater reliability for all subscales of both versions of the German QUALIDEM. The degree of inter-rater reliability can be improved by collaborative Qol rating by more than one nurse. The development of a measurement manual with accurate item definitions and a standardized education program for proxy raters is recommended.
authors: German Center for Neurodegenerative Diseases (DZNE), Witten, Germany.
authors: Martin Nikolaus
authors: MN
authors: Dichter
authors: German Center for Neurodegenerative Diseases (DZNE), Witten, Germany.
authors: Christian G G
authors: CG
authors: Schwab
authors: School of Nursing Science, Witten/Herdecke University, Witten, Germany.
authors: Gabriele
authors: G
authors: Meyer
authors: School of Nursing Science, Witten/Herdecke University, Witten, Germany.
authors: Sabine
authors: S
authors: Bartholomeyczik
authors: German Center for Neurodegenerative Diseases (DZNE), Witten, Germany.
authors: Olga
authors: O
authors: Dortmann
authors: German Center for Neurodegenerative Diseases (DZNE), Witten, Germany.
authors: Margareta
authors: M
authors: Halek
mesh_terms: D000368:Aged; D003258:Consumer Behavior / Q000706:statistics & numerical data; D003704:Dementia / Q000175:diagnosis / Q000453:epidemiology / Q000523:psychology / Q000628:therapy; D005260:Female; D015577:Geriatric Assessment / Q000379:methods; D005858:Germany / Q000453:epidemiology; D006707:Homes for the Aged / Q000592:standards; D006801:Humans; D008134:Long-Term Care / Q000379:methods / Q000523:psychology / Q000592:standards; D008297:Male; D009735:Nursing Homes / Q000592:standards; D017063:Outcome Assessment, Health Care; D019727:Proxy / Q000523:psychology / Q000706:statistics & numerical data; D011594:Psychometrics / Q000379:methods; D011788:Quality of Life; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires