The Silhouettes Fatigue Scale: a validity study with individuals with physical disabilities and chronic pain.

Purpose: Fatigue is known to interfere with function in individuals with physical disabilities. In order to monitor changes in fatigue over time and evaluate the efficacy of treatments, psychometrically sound measures of fatigue are needed. The aim of this work was to evaluate the validity of the Silhouettes Fatigue Scale with English instructions (SFS-EN) in a sample of adults with physical disabilities living in the USA. Methods: Individuals with medical conditions associated with physical disabilities responded to an online survey that included the SFS-EN as well as another validated measure of fatigue (PROMIS short form-4a Fatigue Scale), and measures of pain intensity and pain catastrophizing. Results: 523 individuals participated (mean age ¼ 59.1 years; SD¼11.4). Most participants were Caucasian (89%), women (59%) and unemployed (71%). Results showed strong positive correlations between both measures of fatigue, supporting the convergent validity of the SFS-EN. In addition, the magnitude of this association was significantly greater than the association between the scores of the SFS-EN and the measures of pain intensity and pain catastrophizing, supporting the former’s discriminant validity. Conclusions: The findings extend previous results supporting the SFS as a brief, easy to administer and understand, and valid measure of fatigue