Background. There has been limited research comparing the efficacy of different fatigue rating
scales for use with individuals with chronic fatigue syndrome (CFS). This investigation explored
relationships between two commonly-used fatigue rating scales in CFS research, the Fatigue Scale
and the Fatigue Severity Scale. Theoretically, these scales have been described as measuring
different aspects of the fatigue construct. The Fatigue Scale was developed as a measure of the
severity of specific fatigue-related symptoms, while the Fatigue Severity Scale was designed to assess
functional outcomes related to fatigue.
Methods. Associations of these scales with the eight definitional symptoms of CFS and with eight
domains of functional disability were examined separately in: (1) an overall sample of individuals
with a wide range of fatigue severity and symptomatology; (2) a subsample of individuals with CFS-like symptomatology, and, (3) a subsample of healthy controls.
Results. Findings revealed that both scales are appropriate and useful measures of fatigue-related
symptomatology and disability within a general population of individuals with varying levels of
fatigue. However, the Fatigue Severity Scale appears to represent a more accurate and
comprehensive measure of fatigue-related severity, symptomatology, and functional disability for
individuals with CFS-like symptomatology.