Diagnosing chronic fatigue syndrome (CFS or ME/CFS) is difficult, and we still don't have a single definitive test for it. Doctors have to make a diagnosis by first excluding other conditions, then by considering the full range of symptoms reported by the patient.
The Canadian criteria for diagnosing ME/CFS covers more symptoms, and in more specific terms, than does the U.S. criteria as defined by the CDC. Because of that, many advocates in the United States are calling for the CDC to adopt the Canadian criteria.
The U.S. criteria come from what's generally called "the Fukuda definition," named for the lead researcher on the project to define chronic fatigue syndrome and research criteria for it. Fukuda is the definition that's been most commonly used by researchers around the world since 1994.
The Current U.S. (Fukuda) Diagnostic Criteria for Chronic Fatigue Syndrome
Medically evaluated, unexplained persistent fatigue that's not due to ongoing exertion, isn't substantially relieved by rest, is of new onset and results in a significant reduction in previous levels of activity.
Four or more of the following symptoms (present for six months or more, but not predating the fatigue):
- Impaired memory or concentration
- Post-exertional malaise (extreme, prolonged exhaustion and sickness following physical or mental activity) lasting 24 hours or more
- Unrefreshing sleep
- Muscle pain
- Joint pain without swelling or redness
- Headaches of a new type or severity
- Sore throat that's frequent or recurring
- Tender cervical (neck) or axillary (armpit) lymph nodes
Canadian Diagnostic Criteria for Chronic Fatigue SyndromeFrom the Canadian Consensus Document:
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 adhere to item 7 [below].
The patient must have a significant degree of new onset, unexplained, persistent, or recurrent physical and mental fatigue that substantially reduces activity level.
- Post-Exertional Malaise and/or Fatigue
An inappropriate loss of physical and mental stamina, rapid muscular and cognitive fatigability, post-exertional malaise and/or fatigue and/or pain and a tendency for other symptoms to worsen. The recovery period is pathologically slow -- usually 24 hours or longer.
- Sleep Dysfunction
Unrefreshing sleep or sleep quality, or rhythm disturbances such as reversed or chaotic sleep rhythms.
A significant degree of pain, which can be in the muscles and/or joints, and is often widespread and migratory. Often, there are headaches of a new type, pattern or severity.
Two or more of the following neurological/cognitive manifestations:
- Impairment of concentration and short-term memory consolidation
- Difficulty with information processing
- Categorizing and word retrieval
- Perceptual and sensory disturbances (such as spatial instability and disorientation, inability to focus vision)
- Ataxia (inability to coordinate muscular movement), muscle weakness or twitching
- Cognitive, sensory or emotional overload, which may cause a crash or anxiety
At least 1 symptom from two of the following categories:
- Autonomic manifestations, including: neurally mediated hypotension, postural orthostatic tachycardia syndrome, delayed postural hypotension, light-headedness, pallor, nausea and irritable bowel syndrome, urinary frequency and bladder dysfunction, palpitations with or without cardiac arrhythmias, exertional dyspnea (difficult or labored breathing)
- Neuroendocrine manifestations, including: subnormal body temperature and marked temperature fluctuation, sweating episodes, recurrent feelings of feverishness and cold extremities, intolerance of extreme heat or cold, marked weight change (anorexia or abnormal appetite), loss of adaptability and worsening of symptoms with stress
- Immune manifestations, including: tender lymph nodes, recurrent sore throat, recurrent flu-like symptoms, general malaise, or new sensitivities to food, medications and/or chemicals.
- Illness persists for at least 6 months
Onset is usually distinct but may be gradual. In children, only 3 months is needed for a diagnosis.
The criteria also state that a small number of patients have no pain or sleep dysfunction but fit no other diagnosis. Those people can be diagnosed with ME/CFS if they had an infectious illness at onset.
These criteria are from the Canadian Consensus Document, which also offers objective measures and biomarkers for doctors to follow and recommends treatments.
- Read an overview the entire Canadian Consesus Document on ME/CFS
- Learn why advocates say the U.S. should adopt this document
- Learn more about how U.S. doctors diagnose chronic fatigue syndrome, including what conditions must be excluded
Carruthers, Bruce M. and Marjorie I. van de Sande. All rights reserved. "Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: A Clinical Case Definition and Guidelines for Medical Practitioners"
Centers for Disease Control and Prevention. All rights reserved. "Diagnosing CFS"