CHRONIC FATIGUE SYNDROME (CFS): CDC DEFINITION

The CDC (Center for Disease Control in Atlanta, Georgia, in the USA) updated its previous working definition of CFS (Holmes, et al) in 1993.  The consensus from the leading CFS researchers and clinicians is that Chronic Fatigue Syndrome is a subset of Chronic Fatigue, which of course is a broader category understood to mean prolonged fatigue. True CFS must be differentiated from prolonged fatigue.

The guidelines for evaluating CFS include a thorough medical history, physical exam, and lab tests before a diagnosis of CFS can be made. According to the CDC, clinically evaluated, unexplained chronic fatigue cases can only be classified as Chronic Fatigue Syndrome if:

1)    Unexplained, persistent fatigue that is of new or definite onset (not lifelong), is not the result of ongoing exertion, is not substantially alleviated by rest, and results in substantial reduction in previous levels of occupational, education, social, or personal activities.

2)    The concurrent occurrence of four or more of the following symptoms: substantial impairment in short-term memory or concentration; sore throat; tender lymph nodes; muscle pain; multi-joint pain without swelling or redness; headaches of a new type, pattern or severity; unrefreshing sleep; and post-exertional malaise lasting more than 24 hours.

3)    These symptoms must have persisted or recurred during 6 or more consecutive months of illness and must not have predated the fatigue.[1]

Furthermore the CDC lists conditions that must be excluded or eliminated as a possibility before a diagnosis of CFS can be given, Therefore, the practitioner must rule out infections, metabolic disorders, endocrine disorders, and cancer. He or she must exclude any other diagnosis that may explain the presence of chronic fatigue, such as untreated hypothyroidism (lowered thyroid function), sleep apnea and narcolepsy, and iatrogenic conditions such as side effects of medication. CFS must be differentiated from diagnosable illnesses that may relapse or may not have completely resolved during treatment, such as some types of malignances, hepatitis B or C virus infection. Also major depressive disorders such as schizophrenia, dementia, bipolar affective disorder, etc, must be ruled out, as must alcohol or other substance abuse, or severe obesity.

The CDC does not condone batteries of tests other than those to exclude other medical explanations for the patient’s fatigue. Only in the setting of protocol based research is this suggested.  These tests include serologic tests for Epstein Barr (once thought to be a prime indicating factor in CFS), enteroviruses, retroviruses, human herpes virus 6, Candida Albicans, tests of immunologic function, including cell population and function studies, and imaging test such as MRI and radionuclide scans.

[1] Fukuda, K et. al. The Chronic Fatigue Syndrome; A Comprehensive approach to its definition and study. Annals of Internal Medicine 1994; 18 (supp.1): 126-33

Tags: