Clinical descriptions of ME/CFS

[1] The pathology of ME/CFS is poorly understood, and it can be a difficult condition to diagnose because there is no standard test, many symptoms are non-specific, and because doctors and patients may be unfamiliar with post-exertional malaise.

[1][2] Subgroup analysis suggests that, depending on the applied definition, CFS may represent a variety of conditions rather than a single disease entity.

[6] The 1994 research guidelines were proposed by the "International Chronic Fatigue Syndrome Study Group", led by the Centers for Disease Control and Prevention.

The clinical evaluation should include:[citation needed] Other diagnostic tests have no recognized value unless indicated on an individual basis to confirm or exclude a differential diagnosis, such as multiple sclerosis.

The Oxford criteria defines CFS as follows: Post-infectious fatigue syndrome also requires evidence of a prior infection.

[9] The Canadian consensus criteria were initiated by Health Canada and published by an international group of researchers in 2003.

[16] Several countries, including Australia[17] and the United Kingdom, have authored clinical guidelines that define ME/CFS based on some or all of the available diagnostic criteria.

[18] As there is no generally accepted test for chronic fatigue syndrome, diagnosis is based on symptoms, history, and ruling out other conditions.

[18] The National Institute for Health and Clinical Excellence (NICE) in England and Wales that in the absence of a biomarker, it is difficult to say one set of criteria is more valid than another.

[22] An examination of the CDC 1994 criteria applied to several hundred patients found that the diagnosis could be strengthened by adding two new symptoms (anorexia and nausea) and eliminating three others (muscle weakness, joint pain, sleep disturbance).