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Determining the Minimal Clinically Important Differences in Activity, Fatigue, and Sleep Quality in Patients with Rheumatoid Arthritis
GEORGE WELLS, TRACY LI, LARA MAXWELL, ROSS MacLEAN, and PETER TUGWELL ABSTRACT. Objective. To determine the minimal clinically important differences (MCID) in the patient-reported outcomes of activity (0–30, number of days of limitation), fatigue (0 = none, 100 = complete), and sleep quality (0 = no problems, 100 = worst case) for patients with rheumatoid arthritis (RA). Methods. Two randomized controlled trials comparing abatacept to placebo in RA patients were considered: ATTAIN (n = 391) and AIM (n = 652). An internal anchor-based approach was used to derive the MCID using the Health Assessment Questionnaire, patient global assessment, and pain as anchors. Minimal important change in activity, fatigue, and sleep were determined by estimating mean changes in these outcomes in patients showing change in a narrow range about the MCID of the internal anchor. Correlation analysis was used to determine the consistency of the changes in the outcomes and anchors, and a Delphi process was used to determine the final MCID values. Results. For the 2 trials, consistent patterns of change for activity, fatigue, and sleep and the internal anchors were found with correlations in the range of 0.5, 0.7, and 0.4, respectively. The mean changes for activity, fatigue, and sleep in a narrow range about the MCID of the 3 internal anchors corresponding to the 2 trials were: 3.4 to 4.3 for activity; 6.7 to 17.0 for fatigue; and 4.1 to 7.3 for sleep. Following the Delphi process the MCID determined were 4 for activity, 10 for fatigue, and 6 for sleep. Conclusion. These MCID for activity limitation, fatigue, and sleep problems can be used in designing clinical trials and providing benchmarks in assessing patient improvement. (J Rheumatol 2007;34:280–9) Key Indexing Terms:
MINIMAL CLINICAL IMPORTANT DIFFERENCE From the Department of Epidemiology and Community Medicine, University of Ottawa; Bristol-Myers Squibb, Princeton, New Jersey, USA: and the Institute of Population Health, University of Ottawa, Ottawa, Ontario, Canada. Supported in part by an unrestricted research grant-in-aid from Bristol-Myers Squibb. G. Wells, PhD, Department of Epidemiology and Community Medicine, University of Ottawa; T. Li, PhD, Bristol-Myers Squibb; L. Maxwell, BSc, Institute of Population Health, University of Ottawa; R. MacLean, MD, Bristol-Myers Squibb; P. Tugwell, MD, MSc, Institute of Population Health, University of Ottawa. Address reprint requests to Prof. G. Wells, Department of Epidemiology and Community Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario KIH 8M5, Canada. Accepted for publication October 15, 2006.
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