Measurement of fatigue in systemic lupus erythematosus: A systematic review

Objective. To systematically review fatigue instruments used in patients with systemic lupus erythematosus (SLE) and to seek consensus on which instruments should be recommended for future studies and which data on comorbid conditions should be reported when evaluating fatigue in patients with SLE. Methods. We used data from Medline and EMBase databases (from January 1970 to June 2006), clinical experts, and bibliographies. Data were extracted independently by 4 authors and reviewed by a working group and larger expert panel to produce a recommendation. Instruments were examined for construct validity, reliability, and responsiveness to change. Correlations between fatigue and some components of the Medical Outcomes Study Short Form 36 (SF-36), disease activity, and comorbidities were reviewed. Results. We identified 34 studies that used 15 fatigue instruments in patients with SLE. The Fatigue Severity Scale (FSS) was used in 56% of the studies. The Systemic Lupus Activity Measure was significantly correlated with fatigue, but the Systemic Lupus Erythematosus Disease Activity Index was not. Fatigue was also correlated with pain, poor quality of sleep, depression, and with each subscale of the SF-36. Conclusion. The working group and expert panel recommend the 9-item FSS for evaluating fatigue in SLE patients. Responsiveness to change of fatigue instruments has not been well established in SLE and needs further study. The panel suggested that an important improvement or response could be a 15% decrease in the FSS. The effect of several important confounding factors of fatigue such as sleep disorders, depression, fibromyalgia, and anemia needs to be collected and reported.