BOX 5-1
Definitions of Chronic Fatigue Syndrome

  International CFS Case Definition, 1994a NICE Guidelines for CFS, 2007b
Duration Duration 6 months or longer 4 months or longer in adults
Fatigue Severe chronic fatigue not explained by any medical or psychiatric diagnosis Fatigue with

•   New or specific date of onset, persistent recurrent, unexplained other conditions

•   Substantially activity level

•   Postexertional malaise or fatigue

Symptoms At least four of the following: At least one of the following:

•   Postexertion malaise lasting more than 24 hours

•   Difficulty in sleeping or insomnia

•   Unrefreshing or nonrestorative sleep

•   Muscle or joint pain without inflammation (swelling) manifested as tenderness on palpation in characteristic soft-tissue areas

•   Substantial impairment of short-term memory or concentration

•   Muscle pain

•   Headaches

•   Pain in joints without swelling or redness

•   Painful lymph nodes that are not enlarged

•   Headaches of a new type, pattern, or severity

•   Sore throat

•   Tender lymph nodes in the neck or armpit

•   Poor mental function, such as difficulty in thinking

•   Sore throat that is frequent or recurring

•   Worsening of symptoms after physical or mental exertion

•   Feeling of being unwell or having influenza-like symptoms

•   Dizziness or nausea

•   Heart palpitations without heart disease

And All other medical conditions have been ruled out.

NOTE: CFS = chronic fatigue syndrome; NICE = National Institute for Health and Clinical Excellence.

aCDC, 1994.

bNHS, 2007.

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