“Doctor, I’m So Tired!” Refining Your Work-up for Chronic Fatigue

CHRONIC FATIGUE: DEFINING THE TERMS
A definition of chronic fatigue syndrome (CFS) was initially published in 1988.³ In subsequent years, the term myalgic encephalomyelitis (ME) became popular. Although the terms are sometimes used interchangeably, ME often refers to patients whose condition is thought to have an infectious cause and for whom postexertional malaise is a hallmark symptom.⁴

CDC criteria. While several sets of diagnostic criteria for CFS have been developed, the most widely used is that of the Centers for Disease Control and Prevention (CDC), published in 1994 (TABLE 1).^5,6 A diagnosis of CFS is made on the basis of exclusion, subjective clinical interpretation, and patient self-report.

When the first 2 criteria—fatigue not due to ongoing exertion or other medical conditions that has lasted ≥6 months and is severe enough to interfere with daily activities—but fewer than 4 of the CDC’s 8 concurrent symptoms (eg, headache, unrefreshing sleep, and postexertion malaise lasting >24 hours) are present, idiopathic fatigue, rather than CFS, is diagnosed.⁶

International Consensus Criteria (ICC). In 2011, the ICC for ME were proposed in an effort to provide more specific diagnostic criteria (TABLE 2).⁷ The ICC emphasize fatigability, or what the authors identify as “post-exertional neuroimmune exhaustion.”

The ICC have not yet been broadly researched. But an Australian study of patients with chronic fatigue found that those who met the ICC definition were sicker and more homogeneous, with significantly lower scores for physical and social functioning and bodily pain compared with those who fulfilled the CDC criteria alone.⁸

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