One of the major difficulties with CFS is that the cause or causes or unknown. Typically, the condition is diagnosed after ruling out other problems which include similar symptoms.
When a patient complains of extreme fatigue, medical practitioners typically run tests to rule out the following problems prior to considering a diagnosis of CFS.
Drug dependence
Endocrine diseases (such as hypothyroidism)
Infections
Muscle or nerve diseases (such as multiple sclerosis)
Other illnesses (such as heart, kidney, liver diseases)
Other immune or autoimmune disorders Psychiatric or psychological illnesses, particularly depression (because the severe fatigue of CFS itself may bring about depression, a diagnosis of depression does not rule out CFS; however, fatigue related to depression alone must be ruled out in order for CFS to be diagnosed
Tumors
Once other more easily identifiable conditions are ruled out, criteria as developed by the Centers for Disease Control and Prevention are applied. To be considered as suffering from Chronic Fatigue Syndrome, a patient must match the following two definitional standards as documented on the web site and in printed materials available through the governmental agency:
1. Have severe chronic fatigue of six months or longer duration with other known medical conditions excluded by clinical diagnosis, and
2. Concurrently have 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
post-exertional malaise lasting more than 24 hours.
In addition, the symptoms must have persisted or recurred during six or more consecutive months of illness and must not have predated the fatigue.