CFS Case Definition

Overview

Chronic fatigue syndrome (CFS) is a debilitating and complex disorder characterized by intense fatigue that is not improved by bed rest and that may be worsened by physical activity or mental exertion. People with CFS often function at a substantially lower level of activity than they were capable of before they became ill. The cause or causes of CFS have not been identified, and no specific diagnostic tests are available. Therefore, a CFS diagnosis requires three criteria:

1. The individual has had severe chronic fatigue for 6 or more consecutive months that is not due to ongoing exertion or other medical conditions associated with fatigue (these other conditions need to be ruled out by a doctor after diagnostic tests have been conducted)
2. The fatigue significantly interferes with daily activities and work
3. The individual concurrently has 4 or more of the following 8 symptoms:
   • post-exertion malaise lasting more than 24 hours
   • unrefreshing sleep
   • significant impairment of short-term memory or concentration
   • muscle pain
   • pain in the joints without swelling or redness
   • headaches of a new type, pattern, or severity
   • tender lymph nodes in the neck or armpit
   • a sore throat that is frequent or recurring

These symptoms should have persisted or recurred during 6 or more consecutive months of illness and they cannot have first appeared before the fatigue.

Other Symptoms Accompanying CFS

While the following symptoms are not part of the CFS case definition and do not contribute to the diagnosis of CFS, some patients may also have these additional symptoms: