Instruments for measuring fatigue in people with rheumatic and musculoskeletal diseases: a systematic review of measurement properties

Objective To summarise the measurement properties of instruments used to assess fatigue in people with rheumatic and musculoskeletal diseases (RMDs). Methods A systematic review (SR) of measurement properties was conducted in children, adolescents/young adults and adults with RMDs, following Joanna Briggs Institute and COSMIN (COnsensus-based Standards for the selection of health Measurement INstruments) guidelines. Searches were performed in Medline, Embase, CINAHL and Cochrane Library. Risk of bias assessment, data extraction and synthesis were conducted independently by two reviewers. Instruments were assessed according to Outcome Measures in Rheumatology (OMERACT) criteria. Results Out of 16 657 records, 109 articles underwent full-text review, and 60 met inclusion criteria. These studies evaluated the psychometric properties of 27 instruments. Most studies focused on construct validity (54/60, 90%) and intermethod reliability (45/60, 75%), with an overall low risk of bias. In contrast, test–retest reliability (13/60, 21.7%) and responsiveness (14/60, 23.3%) were less frequently assessed, but also with an overall low risk of bias. Evidence regarding clinical trial discrimination and thresholds of meaningful change was limited or absent, indicating the need for further research in these domains. Only five instruments—the Functional Assessment of Chronic Illness Therapy (FACIT) Fatigue, the 36-Item Short Form Survey Instrument (SF-36) Vitality, the Bristol Rheumatoid Arthritis Fatigue Multi-Dimensional Questionnaire (BRAF-MDQ), the BRAF Numerical Rating Scales (BRAF-NRS) and the Fatigue Severity Scale (FSS)—were rated as valid, reliable and low risk of bias, fulfilling OMERACT endorsement criteria. Conclusions This SR comprehensively supports the use of several well-validated instruments to assess fatigue, particularly FACIT-Fatigue, SF-36 Vitality, BRAF-MDQ, BRAF-NRS and FSS, in both clinical and research settings. PROSPERO registration number CRD42024507112.