Fatigue in Parkinson's Disease: Measurement Properties of a Generic and a Condition-specific Rating Scale.
CONTEXT: High-quality fatigue rating scales are needed to advance the understanding of fatigue and determine the efficacy of interventions. Several fatigue scales are used in Parkinson's disease, but few have been tested using modern psychometric methodology (Rasch analysis). OBJECTIVES: To examine the measurement properties of the generic Functional Assessment of Chronic Illness Therapy-Fatigue (