Chronic Fatigue Syndrome - Classification

Classification

Notable definitions include:

• CDC definition (1994)—the most widely used clinical and research description of CFS, it is also called the Fukuda definition and was based on the Holmes or CDC 1988 scoring system. The 1994 criteria require the presence of four or more symptoms beyond fatigue, where the 1988 criteria require six to eight.

• The Oxford criteria (1991)—includes CFS of unknown etiology and a subtype called post-infectious fatigue syndrome (PIFS). Important differences are that the presence of mental fatigue is necessary to fulfill the criteria and symptoms are accepted that may suggest a psychiatric disorder.

• The 2003 Canadian Clinical working definition—states: "A patient with ME/CFS will meet the criteria for fatigue, post-exertional malaise and/or fatigue, sleep dysfunction, and pain; have two or more neurological/cognitive manifestations and one or more symptoms from two of the categories of autonomic, neuroendocrine, and immune manifestations; and ".

The different case definitions used to research the illness may influence the types of patients selected for studies, and research also suggests subtypes of patients exist within the heterogeneous illness.

Clinical practice guidelines—with the aim of improving diagnosis, management, and treatment—are generally based on case descriptions. An example is the CFS/ME guideline for the National Health Service in England and Wales, produced in 2007 by the National Institute for Health and Clinical Excellence (NICE).