The Canadian Journal of Diagnosis / September 2006 103 How is CFS diagnosed?

Chronic fatigue syndrome (CFS) is a condi-tion of excessive fatigue, cognitive impair-ment and other varied symptoms. It is classified by the World Health Organization as a disease of the nervous system of unknown etiology and may last months or years, causing severe dis-ability.1 A detailed symptom-specific history is the most helpful tool in characterizing patients with CFS. It is often useful to develop an insight into the patient’s expectations and objec-tives, such as insurance issues, disability claims, etc. There are important alternative causes of chronic fatigue to consider which, if present, would preclude the diagnosis of CFS (Table 1). What investigations should b