Giving meaning to measure: Linking self-reported fatigue and function to performance of everyday activities

Fatigue, a common symptom of cancer patients, particularly those on active treatment, is generally evaluated using self-report methods, yet it remains unclear how self-reported fatigue scores relate to performance of daily activities. This study examines the relationships among self-reported and performance-based measures of function in patients receiving chemotherapy (CT) to link self-reported fatigue measures to self-report, and performance-based measures of function. Self-reported, fatigue using the Functional. Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) and self-reported physical function using the physical, function 10 subscale of the Short Form 36 (SF-36) (PF-10) were measured in 64 patients within 2 weeks of beginning CT (n = 64) and after three cycles of CT (n = 48). Motor and cognitive functions were captured using five self-reported and seven, observed-performance measures at each lime point. Significant correlations between self-reported and observed measures ranged from 0.30 to 0.71. Self-reported fatigue correlated (0.30-0.45) with performance-based function.. FACIT-F scores in the range of 30 and below and PF-10 scores in the range of 50 and, below mere related to an increased difficulty perforating everyday activities. Observed measures of physical performance correlate moderately with self-reported, fatigue and self-reported, physical function. These relationships enable one to begin linking fatigue scores directly to a person's ability to perform everyday activities.