Are chronic fatigue and chronic fatigue syndrome valid clinical entities across countries and health- care settings?
Ian Hickie, Tracey Davenport, Suzanne D. Vernon, Rosane Nisenbaum, William C. Reeves, Dusan Hadzi-Pavlovic, Andrew Lloyd, and the International Chronic Fatigue Syndrome Study Group$
Australian and New Zealand Journal of Psychiatry 2009; 43:2535
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Discussion
Five domains of illness experience were derived empirically from multivariate analyses of large inter- national epidemiological and clinical datasets based on symptom reports of subjects with prolonged fatigue. These domains were robust across cultures and health-care settings and are consistent with the key criteria described in the 1994 international CFS case definition. They are best summarized as: pro- longed fatigue and musculoskeletal pain; impairedneurocognitive function; sleep disturbance; and symptoms suggestive of inflammation. From a psy- chiatric perspective, the only noteworthy variation is one of emphasis on the central role of mood disturbance. There has been a strong tendency in the medical and lay literature on CFS to suggest that depressive symptoms are simply an understandable psychological response to the severity or duration of
disability. These data argue that mood disturbance is a core component.
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The present findings indicate that the core dimensions specified in the 1994 definition have construct validity and do not need to be revised. The International CFS Study Group also recommended that for research purposes, the diag- nosis of CFS should be made using validated instru- ments that allow standardized assessments of the major symptom domains of the illness. The present study supports that recommendation and suggests an empirical diagnostic algorithm similar to that used by the Centers for Disease Control and Prevention [51].
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A great deal of research effort, particularly in mental health aspects of general medical care, continues to focus on whether such chronic fatigue states can be distinguished from other medical and psychiatric diagnoses and also from other similar medically unexplained syndromes (e.g. chronic pain, fibromyalgia, irritable bowel syndrome). We suggest that this international study supports the proposition that chronic fatigue states share a common and stereotyped set of symptom domains, and that these can be readily identified in the community and at all levels of health care. Consequently, it is likely that they share common risk factors, are underpinned by a common pathophysiology, and may respond to common treatment strategies. We also suggest that there is little to be gained by further reorganization of the diagnostic criteria, or the related diagnostic entities. It is time to consider whether chronic fatigue states should be included formally in future interna- tional classification systems both in psychiatry and in general medicine.
Conceptually, the present findings are consistent with the notion that the key symptom phenomena of chronic fatigue states are likely to share common central nervous system mechanisms, independent of any other precipitating illness (e.g. infection) or risk factors (e.g. prior mood disturbance).