Measuring fatigue in rheumatoid arthritis: A cross‐sectional study to evaluate the Bristol Rheumatoid Arthritis Fatigue Multi‐Dimensional questionnaire, visual analog scales, and numerical rating scales

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Abstract
Current patient-reported outcome measures of fatigue in rheumatoid arthritis (RA) have limitations, providing only a global perspective. This study constructed a questionnaire (the Bristol RA Fatigue Multi-Dimensional Questionnaire [BRAF-MDQ]) from 45 preliminary questions derived from analysis of patient interviews and surveys and explored its structure for fatigue dimensions. The BRAF-MDQ and short BRAF numerical rating scales (NRS) and visual analog scales (VAS) for severity, effect, and ability to cope with fatigue were evaluated for validity. Two hundred twenty-nine RA patients with fatigue (VAS score ≥5 of 10) completed preliminary BRAF and comparator fatigue scales. Iterative analyses informed item removal or retention in the BRAF-MDQ and identification of subscales (using Cronbach's alpha for internal consistency and factor analysis to identify dimensions). The BRAF-MDQ and short scales were tested in relation to potentially associated variables for criterion and construct validity (Spearman's correlation). The 20-item BRAF-MDQ had good internal consistency (Cronbach's α = 0.932), criterion validity (correlation with other fatigue scales: r = 0.643-0.813), and construct validity (correlations with disability, mood, helplessness, and pain: r = 0.340-0.627). Factor analysis showed 4 distinct dimensions (physical fatigue, living with fatigue, cognition fatigue, and emotional fatigue), which correlated well with the RA Multidimensional Assessment of Fatigue scale (r = 0.548-0.834). The BRAF VAS and NRS showed similar criterion and construct validity. The BRAF instruments include standardized NRS and VAS for fatigue severity, effect, and coping, are RA specific, and have evidence to support validity. The BRAF-MDQ uniquely measures 4 separate dimensions, which may facilitate development of individually-tailored fatigue management programs.