CASE Lauren C, age 35, presents with fatigue, which she says started at least eight months ago and has progressively worsened. The patient, a clerical worker, says she manages to do an adequate job but goes home feeling utterly exhausted each night.
Lauren says she sleeps well, getting more than eight hours of sleep per night on weekends but less than seven hours per night during the week. But no matter how long she sleeps, she never awakens feeling refreshed. Lauren reports that she doesn’t smoke, has no more than four alcoholic drinks per month, and adheres to an “average” diet. She is too tired to exercise.
Lauren is single, with no children. Although she says she has a strong network of family and friends, she increasingly finds she has no energy for socializing. If Lauren were your patient, what would you do?
Fatigue is a common presenting symptom in primary care, accounting for about 5% of adult visits.1 Defined as a generalized lack of energy, fatigue that persists despite adequate rest or is severe enough to disrupt an individual’s ability to participate in key social and/or occupational activities warrants a thorough investigation.
Because fatigue is a nonspecific symptom that may be linked to a number of medical and psychiatric illnesses or to medications used to treat them, determining the cause can be difficult. In about half of all cases, no specific etiology is found.2This review, which includes the elements of a work-up and management strategies for patients presenting with ongoing fatigue, will help you arrive at the appropriate diagnosis and provide optimal treatment.
CHRONIC FATIGUE: DEFINING THE TERMS
A definition of chronic fatigue syndrome (CFS) was initially published in 1988.3In 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 CDC, published in 1994 (see Table 1).5,6A diagnosis of CFS is made on the basis of exclusion, subjective clinical interpretation, and patient self-report.
When the first two 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 four of the CDC’s eight concurrent symptoms (eg, headache, unrefreshing sleep, and postexertion malaise lasting > 24 h) 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 (see Table 2).7The 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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