Interpretation of change scores in ordinal clinical scales and health status measures: The whole may not equal the sum of the parts

Katz, JacobDepartments of Medicine, Division of Rheumatology/Immunology, and Robert B. Brigham Multipurpose Arthritis and Musculoskeletal Disease Center, Brigham and Women's Hospital, Boston, Massachusetts, United States (author)

LIBRIS-ID:oai:hhs.se:1155790040006056
https://research.hhs.se/esploro/outputs/journalArticle/Interpretation-of-change-scores-in-ordinal/991001484692106056URI
https://doi.org/10.1016/0895-4356(96)00016-9DOI

The objective of this study was to analyze the problem of interpreting change scores of ordinal health status measures for clinical research or practice. Methods used included exploration of the generation of change scores in the physical ability scale of the SF-36, one of the most widely used generic health status instruments. Resulting data are presented as the ranking of items according to baseline score; a percentage of patients with severe difficulty and Rasch analysis provided the same rank order of item difficulty. On the interval scale provided by the Rasch model a concentration of items reflecting moderate difficulty occurred. This “inflates” numerical gains for patients with moderate disability compared to patients with very severe or minor physical disability. Calibration of change scores using patient perception of the level of change in function showed important variation of numerical gains with baseline. We conclude that numerically equal gains may differ in their meaning depending on baseline health status. It is recommended that distribution of baseline health status measures and distribution of responders by baseline status be reported in evaluative studies.

Stucki, GDepartment of Rheumatology and Physical Medicine, University Hospital Zurich, 8091 Zurich, Switzerland (author)
Daltroy, L.Harvard School of Public Health and Harvard Medical School, Cambridge, Massachusetts, USA (author)
Johannesson, MagnusStockholm School of Economics,Handelshögskolan i Stockholm(Swepub:hhs)198@hhs.se (author)
Liang, M. HDepartments of Medicine, Division of Rheumatology/Immunology, and Robert B. Brigham Multipurpose Arthritis and Musculoskeletal Disease Center, Brigham and Women's Hospital, Boston, Massachusetts, United States (author)
Departments of Medicine, Division of Rheumatology/Immunology, and Robert B. Brigham Multipurpose Arthritis and Musculoskeletal Disease Center, Brigham and Women's Hospital, Boston, Massachusetts, United StatesDepartment of Rheumatology and Physical Medicine, University Hospital Zurich, 8091 Zurich, Switzerland (creator_code:org_t)

In:Journal of clinical epidemiology: Elsevier Inc49:7, s. 711-7171878-59210895-4356

By the author/editor: Katz, Jacob; Stucki, G; Daltroy, L.; Johannesson, Mag ...; Liang, M. H

About the subject

MEDICAL AND HEALTH SCIENCES: MEDICAL AND HEAL ...; and Health Sciences; and Health Care Serv ...

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