Validation of the Pittsburgh Fatigability Scale in a mixed sample of adults with and without chronic conditions.

The aim of this study was to validate the Pittsburgh Fatigability Scale in three different groups: adults with multiple sclerosis (n = 65), fibromyalgia (n = 64), and healthy adults (n = 86). Participants completed the Pittsburgh Fatigability Scale and other self-report measures. While findings supported the internal consistency of the Pittsburgh Fatigability Scale (all Cronbach's alpha ⩾ 0.85), standard error of measurement estimates were larger than hypothesized. In addition, while item-level reliability was generally supported, item-total correlations for two items were lower than expected. Convergent and discriminant validity were supported, and the Pittsburgh Fatigability Scale was able to distinguish between individuals with and without chronic disease. Overall, the Pittsburgh Fatigability Scale exhibited acceptable psychometric properties.