Chapter Two, Course WB1032
CFS Case Definition
The International Working Group Research Case Definition of CFS (Fukuda et al., 1994) and clarifications published in 2003 (Reeves et al.), as noted earlier, provide the current international standard for diagnosis of CFS in research studies and provide appropriate guidelines for clinical diagnosis. CDC has recently published an empirical case definition that addresses both clinical and research needs (Reeves et al., 2005).
As previously mentioned, CFS has no characteristic physical signs or diagnostic laboratory findings or abnormalities. Diagnosis of CFS involves careful evaluation of symptoms and ruling out or treating other possible causes of the patient’s complaints. The diagnosis of CFS requires that people report severe persistent or relapsing fatigue of at least 6 months duration. This fatigue represents profound mental and physical exhaustion that is not relieved by rest. It is not the typical fatigue that people frequently experience after strenuous physical activity, a difficult work week or other episodes of unusual stress. To qualify for diagnosis, CFS must cause significant reduction in the patient’s previous ability to perform one or more aspects of daily life (work, household, recreation or school). Health care professionals who are evaluating people with CFS should remember that, in spite of their profound disability, many people with CFS do not appear physically ill. In addition to fatigue, the illness must include at least 4 of the 8 symptoms specified in Table 1. Most people with CFS report unusual postexertional fatigue, unrefreshing sleep, and difficulty with memory/concentration; the other symptoms occur in varying proportions, as reported by people with CFS. Of note, unusual postexertional malaise is not resolved by rest and is not limited to fatigue. Most CFS patients report that fatigue and other symptoms (especially concentration/memory problems and pain) are worsened by previously well-tolerated physical or mental activity.
CFS patients may report many other symptoms that are not part of the case definition, such as allergies or sinus problems, numbness or tingling, feeling “in a fog,” dizziness and balance problems, sensitivity to substances and stimuli, and night sweats (Nisenbaum et al., 2004). These complaints may contribute to overall morbidity in the patient, but they are not part of the CFS case definition. Health care professionals should investigate the possibility of underlying medical and psychiatric disorders or natural explanations, such as menopause, in those patients who report numerous symptoms not included in the case definition and should remain alert to the development of new symptoms that may require further evaluation.
Content Source: National Center for Zoonotic, Vector-Borne, and Enteric Diseases (ZVED)