U.S. Case Definition of Chronic Fatigue Syndrome

SummaryIn 1994, researchers from the U.S. Centers for Disease Control and Prevention developed a revised case definition of chronic fatigue syndrome (CFS) (1), a complex illness characterized by debilitating fatigue and a number of accompanying flu-like symptoms. Although Fukuda and associates intended to resolve complexities surrounding the classification of individuals with CFS stemming from previous definitional criteria (1), significant problems with the revised criteria endure. This article highlights reliability issues and other conceptual and operational difficulties inherent in the current U.S. definition of CFS (1). We employ case studies derived from a community-based epidemiological study of chronic fatigue syndrome (2) to illustrate examples of the potential for misclassification of individuals with CFS using the current U.S. criteria (1). Moreover, we suggest alternative approaches to classification and ways to operationalize specific concepts embedded in the current U.S. criteria (1).