Minimal clinically important difference for 7 measures of fatigue in patients with systemic lupus erythematosus.
OBJECTIVE
To determine the minimal clinically important difference (MCID) for 7 measures of fatigue in patients with systemic lupus erythematosus (SLE).


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).


CONCLUSIONS
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.
Goligher
Ewan C
EC
Division of Rheumatology, Immunology, and Allergy, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
Pouchot
Jacques
J
Brant
Rollin
R
Kherani
Raheem B
RB
Aviña-Zubieta
J Antonio
JA
Lacaille
Diane
D
Lehman
Allen J
AJ
Ensworth
Stephanie
S
Kopec
Jacek
J
Esdaile
John M
JM
Liang
Matthew H
MH
D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D003627:Data Interpretation, Statistical; D004185:Disability Evaluation; D005221:Fatigue / Q000175:diagnosis* / Q000209:etiology / Q000523:psychology; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000150:complications / Q000175:diagnosis* / Q000523:psychology; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires