International Consensus Criteria

The Myalgic Encephalomyelitis International Consensus Criteria is a medical case definition.

Background and purpose
The 2012 ICC is very clear on the topic of names:

Problem

The label ‘chronic fatigue syndrome’ (CFS), coined in the 1980s, has persisted due to lack of knowledge of its etiologic agents and pathophysiology. Misperceptions have arisen because the name ‘CFS’ and its hybrids ME/CFS, CFS/ME and CFS/CF have been used for widely diverse conditions. Patient sets can include those who are seriously ill with ME, many bedridden and unable to care for themselves, to those who have general fatigue or, under the Reeves criteria, patients are not required to have any physical symptoms. There is a poignant need to untangle the web of confusion caused by mixing diverse and often overly inclusive patient populations in one heterogeneous, multi-rubric pot called ‘chronic fatigue syndrome’. We believe this is the foremost cause of diluted and inconsistent research findings, which hinders progress, fosters scepticism, and wastes limited research monies.

Solution

The rationale for the development of the ICC was to utilize current research knowledge to identify objective, measurable and reproducible abnormalities that directly reflect the interactive, regulatory components of the underlying pathophysiology of ME. Specifically, the ICC select patients who exhibit explicit multi-systemic neuropathology, and have a pathological low threshold of physical and mental fatigability in response to exertion. Cardiopulmonary exercise test- retest studies have confirmed many post-exertional abnormalities. Criterial symptoms are compulsory and identify patients who have greater physical, cognitive and functional impairments. The ICC advance the successful strategy of the Canadian Consensus Criteria (CCC) of grouping coordinated patterns of symptom clusters that identify areas of pathology. The criteria are designed for both clinical and research settings.

1. Name: Myalgic encephalomyelitis, a name that originated in the 1950s, is the most accurate and appropriate name because it reflects the underlying multi-system pathophysiology of the disease. Our panel strongly recommends that only the name ‘myalgic encephalomyelitis’ be used to identify patients meeting the ICC because a distinctive disease entity should have one name. Patients diagnosed using broader or other criteria for CFS or its hybrids (Oxford, Reeves, London, Fukuda, CCC, etc.) should be reassessed with the ICC. Those who fulfill the criteria have ME; those who do not would remain in the more encompassing CFS classification. (bold emphasis mine)

2. Remove patients who satisfy the ICC from the broader category of CFS. The purpose of diagnosis is to provide clarity. The criterial symptoms, such as the distinctive abnormal responses to exertion can differentiate ME patients from those who are depressed or have other fatiguing conditions. Not only is it common sense to extricate ME patients from the assortment of conditions assembled under the CFS umbrella, it is compliant with the WHO classification rule that a disease cannot be classified under more than one rubric. The panel is not dismissing the broad components of fatiguing illnesses, but rather the ICC are a refinement of patient stratification. As other identifiable patient sets are identified and supported by research, they would then be removed from the broad CFS/CF category.

Research on ME: The logical way to advance science is to select a relatively homogeneous patient set that can be studied to identify biopathological mechanisms, biomarkers and disease process specific to that patient set, as well as comparing it to other patient sets. It is counterproductive to use inconsistent and overly inclusive criteria to glean insight into the pathophysiology of ME if up to 90% of the research patient sets may not meet its criteria (Jason 2009). Research on other fatiguing illnesses, such as cancer and multiple sclerosis (MS), is done on patients who have those diseases. There is a current, urgent need for ME research using patients who actually have ME. (bold emphasis mine)

4. Research confirmation: When research is applied to patients satisfying the ICC, previous findings based on broader criteria will be confirmed or refuted. Validation of ME being a differential diagnosis, as is multiple sclerosis (MS), or a subgroup of chronic fatigue syndrome, will then be verified.

5. Focus on treatment efficacy: With enhanced understanding of biopathological mechanisms, biomarkers and other components of pathophysiology specific to ME, more focus and research emphasis can target expanding and augmenting treatment efficacy.

International Consensus Primer (ICP)
Problem

Overly inclusive criteria have created misperceptions, fostered cynicism and have had a major negative impact on how ME is viewed by the medical community, patients, their families, as well as the general public. Some medical schools do not include ME in their curriculum with the result that very significant scientific advances and appropriate diagnostic and treatment protocols have not reached many busy medical practitioners. Some doctors may be unaware of the complexity and serious nature of ME. Patients may go undiagnosed and untreated; they may be shunned or isolated.

World Health Organisation
The World Health Organisation lists ME and post viral fatigue syndrome under neurological conditions. http://apps.who.int/classifications/icd10/browse/2016/en#/G93.3

Importantly, it doesn’t include chronic fatigue syndrome there, or ME/CFS or CFS/ME. Fatigue syndromes are listed in ‘Other neurotic disorders’ http://apps.who.int/classifications/icd10/browse/2016/en#/F48.0

Comparison with other criteria

 * Norwegian researchers compare the main criteria (Oxford, Fukuda, Canadian, International Consensus and SEID). They say "it is important to distinguish between myalgic encephalomyelitis and chronic fatigue syndrome” to improve understanding of the disease, treatment and patients’ lives, as using incorrect criteria can lead to incorrect treatment.


 * 'Scientists must agree on classifying patients’ Leonard Jason


 * Frank Twisk explains that ME and CFS are "distinct, partially overlapping, clinical entities such as ME and CFS"Frank Twisk 2016
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