revision of the definition was made by the CDC and an international study group in 1994. Patients must see a health provider to be evaluated clinically, they must not have another diagnosis that would explain their condition (although chronically being tired is common with some illnesses). Furthermore the patients must have long term unexplained, persistent or relapsing fatigue plus at least four or more specifically defined associated symptoms; the requirement for any physical finding was removed.
Requiring fatigue to be "unexplained" despite clinical evaluation should exclude most patients with well recognized diseases.The diseases that are most commonly missed are various connective tissue diseases, like some arthritis or lupus conditions, thyroid disease, Lyme disease, and viral illnesses. BioReference Laboratories, Inc has developed a fairly comprehensive evaluation of these conditions to help women understand if they have chronic fatigue or one of the treatable disorders that can cure the exhaustion and fatigue that they are experiencing.