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Validation of the relevant outcome scale for Alzheimer's disease: a novel multidomain assessment for daily medical practice

Vjera A Holthoff12*, Steven Ferris3, Ralf Ihl45, Philippe Robert6, Bengt Winblad7, Serge Gauthier8, Kati Sternberg9 and Frank Tennigkeit10

Author Affiliations

1 Old Age Psychiatry and Cognitive Neuropsychiatry, University Hospital Carl Gustav Carus, University of Technology, Fetscherstraße 74, Dresden 01307, Germany

2 DZNE, German Center for Neurodegenerative Diseases, Dresden, Germany

3 Alzheimer's Disease Center, New York University Langone Medical Center, 550 First Avenue, New York, NY 10016, USA

4 Clinic of Geriatric Psychiatry and Psychotherapy, Alexian Krefeld GmbH, Diessemer Bruch 81, Krefeld 47805, Germany

5 University of Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany

6 Memory Center EA CoBTek, Université de Nice Sophia Antipolis, Hôpital de Cimiez, 4 av Victoria 06000, Nice, France

7 Karolinska Institutet Alzheimer Disease Research Center, Novum 5th Floor, SE-141 86 Stockholm, Sweden

8 Alzheimer's Disease Research Unit, McGill Centre for Studies in Aging, 6825 LaSalle Boulevard, Verdun, Quebec H4H 1R3, Canada

9 Merz Pharmaceuticals GmbH, Eckenheimer Landstraße 100, Frankfurt 60318, Germany

10 AC Immune SA, PSE Building B - EPFL, CH-1015 Lausanne, Switzerland

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Alzheimer's Research & Therapy 2011, 3:27  doi:10.1186/alzrt89

Published: 14 September 2011

Abstract

Introduction

The Relevant Outcome Scale for Alzheimer's Disease (ROSA) is a new observer rating instrument recently developed for routine medical practice. The validity and reliability of ROSA as well as sensitivity to changes due to intervention were examined in an open-label, single-arm, multicenter clinical study in patients with Alzheimer's disease (AD).

Methods

The study enrolled 471 patients with a diagnosis of AD consistent with the criteria of the National Institute of Neurological and Communicative Disease and Stroke/Alzheimer's Disease and Related Disorders Association or with the Diagnostic and Statistical Manual Disorders criteria for dementia of Alzheimer's type. Following assessments of the ROSA and other standard assessments (Alzheimer's Disease Assessment Scale - cognitive subscale, Severe Impairment Battery, Neuropsychiatric Inventory, and Disability Assessment for Dementia), patients were treated with memantine for 12 weeks. Factor analysis of the baseline ROSA total scores was performed based on the principal components method using the varimax orthogonal rotational procedure. The psychometric analyses of the ROSA included internal consistency, test-retest reliability, inter-rater reliability, construct validity, and responsiveness to changes over time.

Results

All items showed adequate factor loadings and were retained in the final ROSA as Factor 1 (all items related to cognition, communication, function, quality of life and caregiver burden) and Factor 2 (all behavior items). The ROSA demonstrated high internal consistency (Cronbach's α = 0.93), test-retest reliability (intraclass correlation coefficient = 0.93), and inter-rater reliability (intraclass correlation coefficient = 0.91). The correlation coefficients between the ROSA and each of the validated scales ranged between 0.4 and 0.7, confirming the ROSA construct validity. Nonsubstantial floor and ceiling effects were found in middle and late disease stages, whereas a small ceiling effect was observed in the early stage. The ROSA responsiveness to change was high (responsiveness index ≥0.8) for all severity stages.

Conclusions

The ROSA is a valid and reliable instrument to aid medical practitioners in sensitively assessing AD-relevant symptoms over time in their clinical practice.