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Structural validity and internal consistency of the Qualidem in people with severe dementia

Published online by Cambridge University Press:  04 September 2017

Alexander M. M. Arons
Affiliation:
Arons Consultancy, Nijmegen, the Netherlands
Roland B. Wetzels*
Affiliation:
Department of Primary and Community Care, Centre for Family Medicine, Geriatric Care and Public Health, Radboud University Medical Center, Nijmegen, the Netherlands Pleyade, Elderly Care Organization, Arnhem, the Netherlands
Sandra Zwijsen
Affiliation:
Department of General Practice and Elderly Care Medicine, VU University Medical Center, Amsterdam, the Netherlands
Hilde Verbeek
Affiliation:
Department of Health Services Research CAPHRI School for Public Health and Primary Care, Maastricht University, Maastricht, the Netherlands
Geertje van de Ven
Affiliation:
FWG, Research & Development, Utrecht, the Netherlands
Teake P. Ettema
Affiliation:
SHDH, Haarlem, the Netherlands
Raymond T. C. M. Koopmans
Affiliation:
Department of Primary and Community Care, Centre for Family Medicine, Geriatric Care and Public Health, Radboud University Medical Center, Nijmegen, the Netherlands Alzheimer Centre, Radboud University Medical Center, Nijmegen, the Netherlands Joachim en Anna, Center for Specialized Geriatric Care, Nijmegen, the Netherlands
Debby L. Gerritsen
Affiliation:
Department of Primary and Community Care, Centre for Family Medicine, Geriatric Care and Public Health, Radboud University Medical Center, Nijmegen, the Netherlands Alzheimer Centre, Radboud University Medical Center, Nijmegen, the Netherlands
*
Correspondence should be addressed to: Roland B. Wetzels, MD, PhD Dept. of Primary and Community Care, Centre for Family Medicine, Geriatric Care and Public Health Radboud university medical center, P.O. Box 9101, 6500, HB, Nijmegen, the Netherlands. Phone: 024-3613338; Fax: 024-3619553. Email: roland.wetzels@radboudumc.nl.

Abstract

Background:

Since its development, the Qualidem has had items that were considered unsuited for people with very severe dementia. This study attempted to investigate the applicability of all Qualidem items in people with all stages of dementia severity.

Methods:

Four data sets that contained Qualidem observations on people with dementia were combined. Dementia severity was categorized based on the Global Deterioration Scale (GDS), with a dichotomization of very severe dementia (GDS 7) and others (GDS 1–6). Unidimensional latent-trait models (Mokken scaling) were estimated to fit the Qualidem responses in the overall sample and the dichotomized groups. Scalability was assessed using coefficients of homogeneity (Loevinger's H), while reliability was assessed with Cronbach's α and ρ.

Results:

Combining the four databases resulted in 4,354 Qualidem measurements. The scalability of all scales was considered acceptable in the overall sample, as well is in the subgroups (all H > 0.3). Additionally, the reliability was good–excellent in the scales: “positive affect,” “positive self-image,” “care relationship,” and “negative affect.” Reliability was questionable–acceptable for “feeling at home,” “social relations,” “social isolation,” and “restless tense behavior.” Reliability was poor for “having something to do.”

Conclusions:

Statistical considerations allow using all Qualidem items in all dementia stages. Future research should determine balance of statistical- versus conceptual-based reasoning in this academic debate.

Type
Research Article
Copyright
Copyright © International Psychogeriatric Association 2017 

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