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Rationale for Revising the CFS Case Definition
The research definition devised in 1988 was made deliberately narrow with the understanding that, while some cases of chronic fatigue syndrome (CFS) might be missed, those cases that met the criteria would provide the best chance for identifying distinguishing features of the disorder. That was a sound strategy within limits, but its application in a variety of studies has now clearly failed to identify any traits that reliably discern CFS patients from healthy controls. The original case definition had at least one other major shortcoming, in that it failed to provide any guidelines for performing comparative studies of CFS with other illnesses marked by severe chronic fatigue.
To address these problems, an international panel of CFS researchers was convened in 1993 to revise the 1988 research case definition and to recommend guidelines for studies of CFS. These new guidelines present a research strategy for evaluation, classification, and subgrouping of fatigued persons. In essence, patients with fatigue of recent onset are classified as having prolonged fatigue (persistent or relapsing fatigue of one month or longer), idiopathic chronic fatigue (six months or longer), and CFS (persistent or relapsing fatigue of six months or longer, with no medical explanation, and meeting specific symptom criteria). Persons can be further subgrouped by type of onset (gradual or sudden), the presence or absence of co-morbid (co-existing) conditions (including psychiatric conditions), fatigue levels, duration of fatigue, current level of physical function, and other epidemiologic or laboratory criteria of interest.
The guidelines also recommend specific medical evaluations for exclusionary diagnoses and the use of specific instruments to evaluate neuropsychiatric conditions, fatigue levels, and overall function.
Page last modified on May 5, 2006
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