Terminology and concepts

International terminological differences exist. The terminology used may reflect incidental factors such as specialty of clinician, historical or social factors - all of which can influence different recording practices both nationally and internationally. The terms used derive from the following:

• The apparent trigger (eg Post-viral fatigue syndrome).
• The research/surveillance definition (Chronic fatigue syndrome).
• A clinically characterized entity falling short of CFS criteria ([idiopathic] chronic fatigue). All terms focus on fatigue, even though the patient experience may go well beyond this single symptom.
• An historical term implying a particular locus and process of disease (ME, [benign] myalgic encephalomyelitis/encephalopathy). This term has also been incorporated emblematically into lay parlance; it is used by many as synonymous with CFS but is also used by some to designate a discrete entity.
• A different historical term derived from an earlier model of disorders of nervous system dysfunction (neurasthenia), which is now rarely used clinically in the UK but remains popular in many countries.

The terms ‘Post-viral fatigue syndrome’ and ‘(benign) myalgic encephalomyelitis’ (classified under G93.3 ‘neurological disorders’) have been used where there is excessive fatigue following a specific trigger such as a viral disease and/or where the symptoms do not fulfil the criteria for F48.0. ‘Fatigue syndrome’, both chronic and not, with or without an established physical precursor, has been classified under ‘neurasthenia’, F48.0. In practice, there is extensive overlap in symptoms (up to 96%).

In the absence of a simple biological marker or test, the diagnosis of CFS and other fatigue states requires the fulfilment of clinical criteria.

The research/surveillance definition for CFS has enabled better characterization of this disorder; however, it implies a distinction from other fatigue states that may be artefactual, since research has shown considerable overlap in the symptoms of many chronic fatigue states. The approach to clinical management is similar for these fatigue states, although differences in severity and type influence the level and model of management used.

Fatigue states associated with other medical conditions, such as inflammatory, autoimmune or malignant disorders, may have clinical similarities, and may respond similarly to treatment, usually aimed at perpetuating factors such as poor sleep, depression and lack of exercise. Likewise, fatigue and other symptoms can characterize certain mental health disorders.

Last edited: 20/1/2004

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