Complications in operationalizing lifelong fatigue as an exclusionary criterion.

The case definitions for chronic fatigue syndrome (CFS) and chronic fatigue syndrome/Myalgic Encephalomyelitis (ME) stipulate that the experience of lifelong fatigue is an exclusionary criterion (Carruthers et al., 2003 ; Fukuda et al., 1994 ). This article examines the lifelong fatigue construct and identifies potential validity and reliability issues in using lifelong fatigue as an exclusionary condition. Participants in the current study completed the DePaul Symptom Questionnaire (Jason et al., 2010 ), and responses were examined to determine if they had experienced lifelong fatigue. This article discusses the extensive process that was needed to confidently discern which participants had or did not have lifelong fatigue. Using the most rigorous standards, few individuals were classified as having lifelong fatigue. In addition, those with and without lifelong fatigue had few significant differences in symptoms and functional areas. This article concludes with a recommendation that lifelong fatigue should no longer be used as an exclusionary criterion for CFS or ME/CFS.