Measuring fatigue in rheumatoid arthritis: a systematic review of scales in use.

OBJECTIVE Fatigue is an important outcome for patients with rheumatoid arthritis (RA). The purpose of this study was to identify the scales being used to measure RA fatigue, and to systematically examine the evidence for their validation. METHODS Articles measuring fatigue in RA were sought using the terms RA and fatigue, and RA and tiredness, plus scale, questionnaire, inventory, and checklist. Index articles reporting identifiable RA fatigue data were examined for the fatigue scale used. Index and validation articles for each scale were reviewed for evidence supporting scale validation to measure RA fatigue using a standardized checklist of content, face, criterion, and construct validity, reliability, and sensitivity to change. RESULTS A total of 61 index articles used 23 different fatigue scales to measure RA fatigue on 71 occasions. Seventeen scales had either no data on validation in RA or limited evidence. Reasonable evidence of validation was identified for 6 scales, each also having some evidence of sensitivity to change: ordinal scales, the Short Form 36 vitality subscale, the Functional Assessment of Chronic Illness Therapy Fatigue Scale, visual analog scales (VAS), the Profile of Mood States, and the RA-specific Multidimensional Assessment of Fatigue scale (MAF). However, the 4 generic scales would benefit from further validation in patients with RA, the VAS requires standardization, and the MAF would benefit from further sensitivity data. CONCLUSION It was possible to identify evidence of reasonable validation for 6 of 23 scales being used to measure RA fatigue. Researchers and clinicians should select scales to measure RA fatigue carefully.