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Minimal Clinically Important Difference for
7 Measures of Fatigue in Patients with
Systemic Lupus Erythematosus
EWAN C. GOLIGHER, JACQUES POUCHOT, ROLLIN BRANT, RAHEEM B. KHERANI, J. ANTONIO AVIÑA-ZUBIETA, DIANE LACAILLE, ALLEN J. LEHMAN, STEPHANIE ENSWORTH, JACEK KOPEC, JOHN M. ESDAILE, and MATTHEW H. LIANG
ABSTRACT. Methods. Study subjects completed 7 fatigue instruments [Fatigue Severity Scale (FSS), Multidimensional Assessment of Fatigue (MAF), Multidimensional Fatigue Inventory (MFI), Vitality scale of the MOS-SF-36, Chalder Fatigue Scale (CFS), Functional Assessment of Chronic Illness Therapy-Fatigue, and a global Rating Scale (RS)] and then participated in a series of interviews with other study participants comparing their fatigue with one another. Each interview participant rated the difference in their fatigue levels on a 7-point transition scale. The MCID was estimated from the mean difference in fatigue scores between each pair of interview participants based on their subjective rating of fatigue contrast. The MCID was also estimated using linear regression modeling. Results. Eighty patients with SLE participated. Patients reported significant levels of fatigue [mean normalized (0 = none, 100 = maximum) fatigue scores for the 7 instruments ranged from 49.8 (CFS) to 71.1 (FSS)]. The MCID of "a little more" fatigue tended to be greater than the MCID for a "little less fatigue" and differed significantly for FSS and MAF. The MCID of normalized scores estimated by linear regression ranged from 7.0 (CFS) to 14.3 (MFI). Conclusion. Fatigue is a common and debilitating component of SLE. Estimates of MCID will help to interpret changes observed in a fatigue score and will be critical in estimating sample size requirements for clinical trials including fatigue as an outcome. (First Release Mar 1 2008; J Rheumatol 2008;35:635-42) Key Indexing Terms:
SYSTEMIC LUPUS ERYTHEMATOSUS
From the Division of Rheumatology, Immunology, and Allergy, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA; Department of Internal Medicine, Hôpital Européen Georges Pompidou, Université René Descartes – Paris V, Paris, France; Arthritis Research Centre of Canada, Division of Rheumatology, University of British Columbia; Centre for Community Child Health Research, Child and Family Research Institute, University of British Columbia; Department of Educational Studies, University of British Columbia; and Department of Health Care and Epidemiology, University of British Columbia, Vancouver, BC, Canada. Supported in part by NIH grant AR47782 and a grant from Rheuminations, Inc. Dr. Goligher was recipient of a Kirkland Summer Student Award. Dr. Aviña-Zubieta holds doctoral fellowship awards from the Canadian Institutes of Health Research, the Michael Smith Foundation for Health Research, The Canadian Arthritis Network, CONACyT-Mexico, and receives support from a Kirkland Scholar Award. Dr. Lacaille holds an Investigator Award from The Arthritis Society. Mr. Lehman was supported by doctoral fellowship awards from the Canadian Institutes of Health Research, the Michael Smith Foundation for Health Research, and the Pfizer Research Fellowship in Arthritis. Dr. Kopec is a Senior Scholar of the Michael Smith Foundation for Health Research. Dr. Esdaile is a Kirkland Scholar. Dr. Liang is the Molson Foundation Arthritis Scholar. E.C. Goligher, MD, Division of Rheumatology, Immunology, and Allergy, Brigham and Women's Hospital and Harvard Medical School; J. Pouchot, MD, Arthritis Research Centre of Canada and Department of Internal Medicine, Hôpital Européen Georges Pompidou, Université René Descartes – Paris V; R. Brant, PhD, Centre for Community Child Health Research, Child and Family Research Institute; R.B. Kherani, MD; J.A. Aviña-Zubieta MD, MSc; D. Lacaille, MD, MHSc; S. Ensworth, MD; J.M. Esdaile, MD, MPH, Arthritis Research Centre of Canada; A.J. Lehman, MA, Arthritis Research Centre of Canada and Department of Educational Studies, University of BC; J. Kopec, MD, PhD, Arthritis Research Centre of Canada and Department of Health Care and Epidemiology, University of BC; M.H. Liang, MD, MPH, Division of Rheumatology, Immunology, and Allergy, Brigham and Women's Hospital and Harvard Medical School and Arthritis Research Centre of Canada. Address reprint requests to Prof. J. Pouchot, Service de Médecine Interne, Hôpital Européen Georges Pompidou, 20 rue Leblanc, 75908 Paris Cedex 15, France. E-mail: jacques.pouchot@egp.aphp.fr Accepted for publication November 28, 2007. |
