Friday 19 May 2023

The Case Definition Quagmire Surrounding ME Remains an Urgent Challenge


"The failure to agree on firm diagnostic criteria has distorted the data base for epidemiological and other research, thus denying recognition of the unique epidemiological pattern of myalgic encephalomyelitis."


- Dr. A. Melvin Ramsay-

What is in a Name, what is in a Case Definition 

One of the biggest debates surrounding Myalgic Encephalomyelitis (ME) concerns the name of the illness and how it is diagnosed. There is no general agreement on a reference standard for diagnosis, and no single diagnostic test available.

The assertion that ME and CFS are different clinical entities is disputed. Both labels are being used interchangeably by patients themselves who believe they are the same thing through no fault of their own.

People with ME are often given a diagnosis of CFS, or even worse Chronic Fatigue, making it look like they are just 'tired' people.
Unfortunately in Ireland and elsewhere some people have been diagnosed with the label CFS despite the ME related symptoms and severities present, where medics mistakenly believe ME and CFS are exactly the same thing. Divergent and obscure definitions of what 'CFS' really is, or isn't, have intermingled with a distinct disease, ME, which is well defined by history, clinical observation and has a clear listing in the International Classification of Diseases (ICD) since 1969.

We recognize four categories of case definitions: ME, CFS, ME/CFS, SEID. These labels reflect very different case definitions. 
  • The first category comprises two ‘ME’ case definitions: ME as per Ramsay, and ME according to the International Consensus Criteria (ME-ICC). The case definition of ME Ramsay  is very simple requiring only two types of symptoms: muscle fatigability/post-exertional muscle weakness and specific neurological symptoms. In contrast, the ME-ICC case definition is much more complex.

  • The other three categories comprises several case definitions including Holmes 1988, Oxford 1991, Fukuda 1994, CCC 2003, NICE 2007, Revised CCC 2010, SEID 2015, NICE 2021

Solving the current confusion with regard to case definitions requires a clear distinction between ME, ME-ICC, CFS, ME/CFS, and SEID.

Currently, a range of different definitions exist, diagnostic criteria which focus on similar sets of symptoms, but differ markedly in the number of symptoms required and how those symptoms are defined. Each definition is different, sometimes subtly, so the terms ME, CFS and their various combinations (ME/CFS, CFS/ME) mean different things to different people, and therein lies a worldwide case definitional quagmire surrounding ME and CFS which currently in 2023 remains an urgent challenge. 

The operational ambiguity has important consequences for research in ME, as different studies operationalize the criteria in different ways, limiting comparisons across studies. Having different case definitions also has resulted in diagnostic unreliability and confusion for clinicians, patients, and their families.

Other chronic illnesses, such as rheumatoid arthritis and systemic lupus, have previously overcome similar case definition difficulties, so with further funding, data collection and research it is possible in an illness like ME. 

Outlining the various case definitions being used worldwide will hopefully shed light on why there is so much confusion around ME, and highlight the fact that the label and criteria use is key.

Before we summarise various case definitions let's look at an important area:

  • The differences between Myalgic Encephalomyelitis (ME) and the later named Chronic Fatigue Syndrome (CFS) following the outbreak of an ME-similar illness in the US in the 1980s here

Case Definitions

The ME community and Myalgic Encephalomyelitis (ME) has been undermined by lax criteria that contribute to increased misdiagnoses and contribute to ongoing discrimination, gaslighting and stigma suffered by those with ME. 

The Oxford (UK), Fukuda (US) and NICE 2007 (UK) criteria should not be used to diagnose ME, and research studies on ME should not include those criteria nor people diagnosed with them. 

As well as the International Consensus Criteria (ICC) the less undermining diagnostic criteria currently available are the Canadian Consensus Criteria and the Institute of Medicine (NAM) Criteria (SEID). We give a brief summary of different criteria below but go into more detail with the SEID criteria to highlight what is not right with using SEID to diagnose ME.

Ramsey (UK) 1986

The first outbreak of Myalgic Encephalomyelitis (ME) was recorded in 1934 but the term Myalgic Encephalomyelitis first appeared in the medical literature in 1956 when it was named by Dr. Melvin Ramsay.

In 1956, ME pioneer Dr. Melvin Ramsay formally coined Sir Donald Acheson's selected name for the disease myalgic encephalomyelitis in a paper describing the 1955 epidemic among staff at Royal Free Hospital in London. 

The Ramsay Definition for Myalgic Encephalomyelitis (1986) - “A syndrome initiated by a virus infection, commonly in the form of a respiratory or gastrointestinal illness with significant headache, malaise and dizziness sometimes accompanied by lymphadenopathy or rash. Insidious or more dramatic onsets following neurological, cardiac or endocrine disability are also recognised. 

Characteristic features include:

(1) A multisystem disease, primarily neurological with variable involvement of liver, cardiac and skeletal muscle, lymphoid and endocrine organs.

(2) Neurological disturbance – an unpredictable state of central nervous system exhaustion following mental or physical exertion which may be delayed and require several days for recovery; an unique neuro-endocrine profile which differs from depression in that the hypothalamic/pituitary/adrenal response to stress is deficient; dysfunction of the autonomic and sensory nervous systems; cognitive problems.

(3) Musculo-skeletal dysfunction in a proportion of patients (related to sensory disturbance or to the late metabolic and auto immune effects of infection)

(4) A characteristically chronic relapsing course."

ME-Ramsay is a neuromuscular disease. The discriminative symptom of ME is muscle fatiguability/prolonged muscle weakness following trivial exertion. Ramsay states: “In my opinion a diagnosis should not be made without it”. Muscle fatigability is accompanied by “neurological disturbance, especially of cognitive, autonomic and sensory functions”.
The case definition of ME by Ramsay is very simple and requires two types of symptoms: muscle fatigability/post-exertional muscle weakness and specific neurological symptoms.
 “Other characteristics include [..] a prolonged relapsing course and variation in intensity of symptoms within and between episodes, tending to chronicity.”

Dr. Ramsay, together with Dr. Elisabeth Dowsett, listed this criteria for ME in 1990 in the same article (just prior to his death):

"We adopted the following criteria:

A syndrome initiated by a viral infection commonly described as a respiratory/gastro intestinal illness but a gradual or more dramatic onset following neurological, cardiac or endocrine disability is recognised.

"The cardinal features, in a patient who has previously been physically and mentally fit, with a good work record are:

(1) Generalised or localised muscle fatigue after minimal exertion with prolonged recovery time.

(2) Neurological disturbance, especially of cognitive, autonomic and sensory functions, often accompanied by marked emotional lability and sleep reversal.

(3) Variable involvement of cardiac and other bodily systems.

(4) An extended relapsing course with a tendency to chronicity.

(5) Marked variability of symptoms both within and between episodes."

Summary: Ramsay's Definition of ME is mostly an immunological/neurological disease

Holmes Criteria (US) 1988

The US Centers for Disease Control and Prevention (CDC) first defined CFS, with great emphasis on the word “fatigue”, in 1988. This definition, referred to as “Holmes”, was later replaced by the 1994 ”Fukuda”, then by the 2005 “Reeves”, and most recently by the 2015 IOM (Institutes of Medicine) report, still emphasizing fatigue. 

Holmes et al coined the term ‘chronic fatigue syndrome’ (CFS) as an alternative to ‘The chronic Epstein-Barr virus syndrome’. It is also called the "Holmes definition", after the manuscript's first author. 
Since this CDC-1988/Holmes Criteria/definition was presented in 1988 numerous revisions have been developed, aiming for distinctive and reliable identification of individuals who represent a homogenous and consistent phenotype of the hypothesised disease entity, consistent with pathophysiological and psychosocial findings. 

The Holmes criteria require these two elements:

  • Debilitating fatigue of new onset which interferes with the patient's daily activities
  • Other fatiguing conditions must be eliminated

They define 11 symptom criteria:

  • Mild fever or chills
  • Sore throat
  • Sore lymph nodes
  • Muscle weakness
  • Muscle discomfort or myalgia
  • Fatigue after exercise lasting at least 24 hours
  • Headaches
  • Joint pain
  • Hypersomnia or insomnia
  • A rapid onset over a few hours or days

And three physical criteria that must be documented by a physician:

  • Low-grade fever
  • Nonexudative pharyngitis
  • Tender lymph nodes

To make a diagnosis, a patient must meet either 8 of the 11 symptom criteria, or 6 of the 11 symptom criteria and 2 of 3 physical criteria.

Problems with Holmes

Over emphasis on fatigue - on degrees or variations of 'fatigue', which is merely one of many symptoms in this disease. Fatigue is also a prevalent symptom in many other diseases and illnesses, as well as a normal physiological state.

Use of CFS label

No emphasis on exertion intolerance, i.e. PENE.

The practice of using the CFS Holmes research definition has flooded the research subject pool with many 'fatiguing illnesses' that  do not necessarily fit the past and current definitions for the neurologically defined disease, ME. This has only served to dilute and muddy research results into a confusion of mixed results.  
This also does a disservice to those patients who do not fit into the category of the current and historic ME definitions.

Summary: Holmes definition is a combination of fatigue narrative and immunological/neurological disease.
Minimum duration before diagnosis is 6 months

Oxford Criteria (UK) 1991
In the UK other criteria were developed for and by a group of psychiatrists, called the Oxford Criteria.

Problems with Oxford

The criteria were developed for and by a group of psychiatrists, and called the Oxford Criteria.

Over emphasis on fatigue - these criteria are far less rigorous and may include patients with fatigue as their only symptom. As you can imagine there are a myriad of illness which can have fatigue as a primary symptom, e.g. MS, Lupus, Fibromyalgia, cancer, heart disease, etc so the possibility for misdiagnosis is very high and the research criteria used results in a toxic mix of patients with a range of illnesses.
The Oxford criteria is not used anywhere else in the world and yet the HSE have previously adopted them straight from the UK as if they are the best way to diagnose people with ME.

Proponents for more restrictive case definitions dismiss findings from treatment studies documenting effects of cognitive behavioural treatment or graded exercise therapy for patients diagnosed with the Oxford-1991 or CDC-1994/Fukuda case definitions. Their claim is that for a more exclusive selection of patients with ME, defined according to specific pathophysiology, the side effects of these treatment modalities are hazardous. 

To further explain how this criteria is viewed by international experts, in July 2016, the Agency for Healthcare, Research and Quality in the USA issued an addendum to its Evidence Report recommending the retirement of the Oxford criteria for ME/CFS because it was the least specific of all the definitions and only included six months fatigue as a primary symptom and did not include Post Exertional Neuroimmune Exhaustion (PENE) which is considered a hallmark of the disease.
The Oxford criteria developed by UK psychiatrists is unfit for use and cannot be reliably extrapolated to people with ME as the distinct neurological indicators of the disease are ignored and excluded.

Summary: Oxford definition is a fatigue narrative
 Minimum duration before diagnosis is 6 months

The Fukuda Criteria (US) 1994
In 1994, Fukuda and colleagues published a case definition for CFS and idiopathic chronic fatigue that was intended to guide research in adult populations. The Fukuda definition defines chronic fatigue as “self-reported persistent or relapsing fatigue lasting 6 or more consecutive months” and requires a clinical evaluation to identify or rule out medical or psychological conditions that could explain the chronic fatigue’s presence.
A diagnosis of CFS requires the absence of exclusionary conditions, severe chronic fatigue, and at least four of eight minor symptoms.

The Fukuda Criteria was developed by the CDC in the USA after the outbreak at Lake Tahoe. The most widely used diagnostic criteria for CFS, Fukuda was led by the CDC. These criteria are named after the first author Keiji Fukuda. 

The 1994 CDC criteria specify the following conditions must be met:

Primary symptoms

Clinically evaluated, unexplained, persistent or relapsing chronic fatigue that is:

  • of new or definite onset (has not been lifelong);
  • is not the result of ongoing exertion;
  • is not substantially alleviated by rest; and
  • results in substantial reduction in previous levels of occupational, educational, social, or personal activities.

The concurrent occurrence of four or more of the following symptoms, all of which must have persisted or recurred during 6 or more consecutive months of illness and must not have predated the fatigue: 
  • self-reported impairment in short-term memory or concentration severe enough to cause substantial reduction in previous levels of occupational, educational, social, or personal activities;
  • sore throat;
  • tender cervical or axillary lymph nodes;
  • muscle pain;
  • multi-joint pain without joint swelling or redness;
  • headaches of a new type, pattern, or severity;
  • unrefreshing sleep;
  • post-exertional malaise lasting more than 24 hours.

Problems with Fukuda

CDC's Fukuda, is a 'CFS' definition that broadens the research subjects to include patients that may not necessarily fit the current and past definitions for ME. The practice of using the CFS Fukuda research definition has flooded the research subject pool with many 'fatiguing illnesses' that  do not necessarily fit the past and current definitions for the neurologically defined disease, ME. This has only served to dilute and muddy research results into a confusion of mixed results.  
This also does a disservice to those patients who do not fit into the category of the current and historic ME definitions

The CFS Fukuda case definition is characterized by vaguely worded criteria that lack operations definition and guidelines to assist health care professionals in their interpretation and application of the diagnostic criteria.

The disease known as CFS, as described by the vague criteria known as Fukuda, was promoted as the only diagnostic criteria to the US medical practitioners with no FDA approved treatments.
These criteria are used to define Chronic Fatigue Syndrome, though the definition does not require what some consider core symptoms of ME such as PENE and neuro-cognitive symptoms. As Post Exertional Neuroimmune Exhaustion (PENE) is not a mandatory criterion under Fukuda you can begin to imagine the number of misdiagnosis and confusion that abounds.
The definition has been criticised for being overly inclusive. Research has indicated that individuals with a primary psychiatric illness, e.g., primary Major Depressive Disorder, may be misdiagnosed under the Fukuda criteria due to many overlapping symptoms including fatigue and sleep difficulties. (Jason et al 1999, 2010)

A major limitation of the Fukuda definition is that its criteria are polythetic, which inevitably leads to great heterogeneity among the group of patients diagnosed according to these criteria. For instance, two patients could have very little symptom overlap yet both be diagnosed with CFS.

The Fukuda criteria places emphasis on fatigue, with neurological signs being minor and optional. Emphasis on variations of 'fatigue', which is only one of many symptoms in this disease. Fatigue is also a prevalent symptom in many other diseases and illnesses.

The Fukuda definition indicates that patients who fail to meet its criteria for fatigue severity and at least four minor symptoms should be diagnosed with idiopathic chronic fatigue.

PEM is one of the minor symptoms in the Fukuda definition.

As mentioned already the Fukuda definition relies on 'fatigue' as its major criterion. For that reason, many patients who fall under this diagnostic label hate the name, they call it the F-word since, for many of them, 'fatigue' per se is not the major problem, and does not best represent how they would explain their condition. 

The Fukuda definition is widely recognised to have a number of limitations, it makes no attempt to differentiate patients on the basis of severity of illness or level of functional disability.

The Fukuda 'CFS' term is an impossibly inclusive diagnostic construct, begging the question, 'Is CFS a recognisable disease entity with a unique pathophysiology, or is it a ragbag of common non-specific symptoms with many causes, mistakenly labelled as a syndrome?'....

....and another question, 'Does everyone with CFS as defined by Fukuda have ME?' In a 2023 study by Vaes, Jason et al, it was found that “… Almost 90% of the participants fulfilled the Fukuda case definition, compared to 80%, 59% and 39% fulfilling the SEID, CCC and ICC case definitions, respectively”, more here.

Summary: Fukuda is a fatigue narrative
Minimum duration before diagnosis is 6 months.

Canadian Consensus Criteria 2003

The pre-runner to the ICC was the Canadian Consensus Criteria (CCC) published by Carruthers et al in 2003.
This criteria was designed to assist health professionals make a diagnosis effectively but, like most ‘definitions’ of ME or CFS, the clinical usefulness has never been formally validated. The Canadian Consensus Criteria was found not to be sensitive, leaving a question mark over its practical usefulness in research or clinical practice, more about that here.

We still know very little about its usefulness in practice, apart from the fact that 50–60% of patients meeting the wider and more vague Fukuda 1994 criteria also meet the Canadian Consensus Criteria, and that these patients have a higher burden of illness.

The CCC criteria defines ME/CFS as an acquired, organic, pathophysiological multi-systemic illness that occurs in both sporadic and epidemic forms and requires core symptoms including post-exertional malaise (PEM) and neurocognitive dysfunction, in contrast to the polythetic approach of the Fukuda case definition.

Because fatigue can be present in many other illnesses, the CCC requires for a diagnosis of ME/CFS the presence of four cardinal symptoms - fatigue, PEM, sleep dysfunction, and pain, as well as other minor symptoms. So, for a diagnosis of ME/CFS, the CCC requires that symptoms be present from the following six symptom categories for 6 months or longer:

  • fatigue, including substantial reduction in activity level;
  • PEM and/or post-exertional fatigue;
  • sleep dysfunction;
  • pain;
  • neurologic/cognitive manifestations;
  • autonomic, neuroendocrine, or immune manifestations

The authors intentionally included more symptoms than had been specified in previous diagnostic criteria to help clinicians identify patients with unique combinations of symptoms, and a symptom merely must be present to count toward a diagnosis.

Problems with CCC 2003

Over emphasis on fatigue again, which is merely one of many symptoms in this disease. Fatigue is also a prevalent symptom in many other diseases and illnesses, as well as a normal physiological state.

Merely requiring a symptom to be present without specifying a minimum level of frequency or severity resulted in more frequent misdiagnosis of healthy controls as having ME/CFS.

The CCC talks of ME and CFS as though they were the same illness, they are not. 

Summary: CCC definition is about an immunological and neurological disease.
 Minimum duration before diagnosis is 6 months.

The Empirical/Reeves Criteria 2005

Reeves tried to elaborate the CDC1994/Fukuda definition. The Reeves case definition led to a tenfold prevalence estimate as compared with the CDC1994/Fukuda definition,probably due to misclassification and inclusion of patients with major depressive disorder. Under the Reeves criteria, patients are not required to have any physical symptoms.

Problems with Reeves

The purpose of rigour had not been achieved, and the Empirical-2005/Reeves case definition was never broadly implemented.

Summary: Fatigue narrative

NICE Clinical Guidelines for ME/CFS (UK) 2007

The British National Institute for Health and Clinical Excellence (NICE) was developed by the National Collaborating Centre for Primary Care, which worked with a group of health care professionals, patients, and caregivers, and technical staff who reviewed the evidence and drafted the recommendations which were finalized after public consultation.
The NICE 2007 criteria for diagnosis require the presence of fatigue and at least one other
symptom, and these symptoms must have persisted for at least 4 months.
Although the NICE criteria require fewer total symptoms relative to other diagnostic criteria for ME/CFS, the guidelines note that PEM or post-exertional fatigue, cognitive difficulties, sleep disturbance, and chronic pain are key features of the illness and that a diagnosis of ME/CFS should be reconsidered if none of these symptoms are present.
As with other criteria, the NICE guidelines recommend that alternative diagnoses be ruled out before a diagnosis of ME/CFS is given.

NICE 2007 Criteria:

• Fatigue (characterized by post-exertional malaise and/or fatigue)
• One or more of the following: – difficulty with sleeping – muscle and/or joint pain – headaches – painful lymph nodes without pathological enlargement – sore throat – cognitive dysfunction – physical or mental exertion makes symptoms worse – general malaise or flu-like symptoms – dizziness and/or nausea – palpitations in the absence of identified cardiac pathology
• Persistence of symptoms for at least 4 months for adults and at least 3 months in children or young people.

Problems with NICE 2007

So many.

Naming ME with 'CFS/ME' and not even 'ME/CFS': the CFS/ME label is used by the psychatric cabal in the UK and elsewhere, with the focus on 'fatigue' placed first in the CFS part.

Over emphasis on fatigue again following from Holmes, Fukuda and Oxford which is merely one of many symptoms in this disease and not the most serious. Fatigue is also a prevalent symptom in many other diseases and illnesses, as well as a normal physiological state, so emphasising fatigue does not explain a multi-system illness.

Suggested therapies such as Graded Exercise (GET) and Cognitive Behavioural Therapy (CBT) are harmful to those with ME.

Symptoms experienced by those with severe/very severe/profound ME not detailed.

Charities and patient groups condemned the guidelines as "unfit for purpose" and various submissions from charities, researchers, patients and advocates led to a review of the 2007 guidelines, see more under the title Criticism and Controversy here.

Minimum duration before diagnosis is 4 months

Revised Canadian Consensus Criteria for ME/CFS (2010)

The Revised CCC was intended to better operationalize the CCC. Authors reviewed previous definitions and literature available; tried to limit the types of symptoms within each of the Canadian Consensus Criteria (2003) categories to allow investigators to more reliably categorize patients.

In 2010, Jason and colleagues revised the CCC and provided explicit rules for applying this case definition, including a questionnaire for assessing symptoms. The authors provided operational definitions for several key symptoms to improve diagnostic reliability and use of the CCC in research studies (Jason et al., 2010, 2013b).
For a diagnosis of ME/CFS, the Revised CCC requires the presence of symptoms from the same six categories (with some wording differences) as those of the original CCC (Jason et al., 2010). The Revised CCC recommends the use of a structured questionnaire (the DePaul Symptom Questionnaire) (DePaul Research Team, 2010) to gather standardized information on symptoms as well as the use of the scales of the Short Form 36-Item Questionnaire (SF-36) of the Medical Outcomes Study to assess whether a patient has a substantial reduction in functioning (McHorney et al., 1993). A symptom must be present with moderate severity about half of the time to meet criteria for a symptom category, and a patient must score below a certain maximum score on at least two of the three scales of the SF-36 to meet criteria for a substantial reduction in functioning.

CCC 2010 criteria require the following symptoms:

• Fatigue • Post-exertional malaise and/or post-exertional fatigue • Unrefreshing sleep or disturbance of sleep quantity or rhythm disturbance • Pain (or discomfort) that is often widespread and migratory in nature • Two or more neurological/cognitive manifestations • At least one symptom from two of the three categories: – autonomic manifestations – neuroendocrine manifestations – immune manifestations • Persistent or recurring symptoms for a least 6 months

Difference between CCC 2003 and 2010 - The CCC requires only the presence of a symptom to count towards a diagnosis, whereas the Revised CCC specifies that minimum levels of frequency and severity be present for a symptom to count towards diagnosis.

Problems with CCC 2010

As above with CCC 2003
Minimum duration before diagnosis is 6 months

International Consensus Criteria (ICC) 2011 & Primer 2012

International Consensus Criteria (ICC) 2011

The International Consensus Criteria (ICC) which insisted that CFS should not be considered a diagnostic entity and that ME is a specific diagnosis requiring thorough patient history, examination, and testing.

Many worldwide experts on Myalgic Encephalomyelitis (ME), including Ireland’s Prof Austin Darragh (RIP) came together and produced comprehensive diagnostic criteria called the International Consensus Criteria (ICC) (2011).

The International Consensus Criteria (ME-ICC) advocates for removing fatigue as a characteristic symptom and defines the disorder as an acquired neurological disease with complex global dysfunctions.

The ME-ICC was developed for both clinical and research use and includes considerations for diagnosing children and adolescents.

The ICC defines specific symptom requirements:
  • post-exertional neuroimmune exhaustion (PENE),
  • neurological impairments (which encompass neurocognitive impairments; pain; sleep disturbance; and neurosensory, perceptual, and motor disturbances);
  • immune,
  • gastrointestinal and genitourinary impairments,
  • energy metabolism impairments.
It is important to note that the 6/4/3-month waiting time for diagnosis as per other case definitions is dropped in the ICC, i.e. there is no minimum time and ME can be diagnosed immediately, a very important thing when we consider that delay in diagnosis prevents relevant management and symptom treatments which inevitably leads to a decline in health with worsening of illness.  
The ICC includes operational notes for each of the symptom criteria.

The ICC alone is not enough to confirm an ME diagnosis, the next step is to absolutely affirm the ME diagnosis. The International Consensus Primer guides doctors to diagnose, treat and rule out other diseases. It is a booklet prepared by ME experts to guide doctors in treating those who fit the ICC.


Comments re the ICC

We recognise that the ME-ICC, nor the ICP, does not provide guidelines on the severity or frequency of symptoms that must be present for a diagnosis (as per Leonard Jason et al., 2013); and that it does not suggest the use of a standardised questionnaire for clinical diagnosis, but we acknowledge that the ICC recommends that all patients in research studies complete the International Symptom Scale to increase the reliability of data collection.

In light of the lack of standardised questionnaire for a clinical diagnosis within the ICC, we suggest that alongside the use of the ICC and ICP that clinicians and patients use the De Paul Symptom and Severity Questionnaire (DSQ-2) as well as the De Paul PEM Questionnaires (the short DSQ-PEM and the longer DPEMQ) to evidence symptoms and severity, and to track changes.
There are also specific paediatric questionnaires available which include both parent and child forms, i.e. the DSQ-PED Parent and Child Forms.

 Myalgic Encephalomyelitis International Consensus Criteria

International Consensus Primer 2012

In 2012, the ICC authors provided a condensed version to offer as physician's guidelines, i.e., the International Consensus Primer (ICP)

The ICP states:  "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 International Consensus Criteria (ICC) because a distinctive disease entity should have one name."

The ICP approach makes sure no patient is seen as too challenging to accurately assess.

The ICP was written to provide clinicians a one-stop, user-friendly reference for ME. It includes a concise summary of current pathophysiological findings upon which the ICC are based. A comprehensive clinical assessment and diagnostic worksheet enables clear and consistent diagnosis of adult and paediatric patients world-wide.

The treatment and management guidelines offer a blueprint for a personalized, holistic approach to patient care, and include non-pharmaceutical and pharmaceutical suggestions. Patient self-help strategies provide recommendations for energy conservation, diet, and more.
Educational considerations for children are included.
The ICP specifically targets primary care clinicians, as well as specialists in internal medicine. Other medical care practitioners may find it helpful.
The ICP stems from wide international research and hundreds of thousands of hours of clinical investigations, all relevant to ME.

Myalgic Encephalomyelitis - Adult & Paediatric International Consensus Primer for Medical Practitioners

NAM/SEID Crieria (US) 2015

Unfortunately the CDC did not accept or adopt the ICC and instead commissioned its own group with limited access to ME information to create their vague 2015 IOM report, minimizing the disease yet again. 

In the US, the National Academy of Medicine (NAM) is a non-profit, non-governmental organization which provides expert advice on issues relating to biomedical science, medicine and health. It was formerly the Institute of Medicine (IOM). The IOM produced a comprehensive report in 2015 called “Beyond Myalgic Encephalomyelitis/chronic fatigue syndrome - Redefining an illness”, which outlined suggestions for an ME/CFS diagnosis based on thousands of medical reports over several decades and a new name for the illness was proposed: Systemic Exertion Intolerance Disease (SEID).

The report goes on to recommend new diagnostic criteria very similar to the CCC-ME of 2003 and lists Post Exertional Malaise as a mandatory criterion for diagnosis.

The NAM/SEID criteria require the following three symptoms:
  • Severe, disabling fatigue of new onset that persists for more than 6 months
  • Post-exertional malaise (PEM)
  • Unrefreshing sleep.

Also, at least one of the following is required:

Problems with SEID

NAM/SEID Criteria does not list Post Exertional Neuroimmune Exhaustion (PENE) as a mandatory criterion for diagnosis.

NAM/SEID Criteria also notes that for all symptoms except orthostatic intolerance, "frequency and severity of symptoms should be assessed," and that these symptoms should be present at least half the time with at least moderate severity

NAM/SEID Criteria is based on the US government commissioned IOM report (IOM: renamed National Academy of Medicine, NAM) to redefine CFS and ME. The report resulted in a definition based mainly on CFS studies, leaving out much of what is known about ME as defined by the ICC - the IOM does NOT describe or define ME.

US health agencies have promoted the NAM definition and use the term SEID. NAM criteria took over the ME/CFS label and has been posted on the CDC website since at least 2018.

A study by Leonard Jason has shown that NAM/SEID Criteria is almost 3 times broader than the existing 1994 CFS Case Definition (Fukuda criteria). NAM/SEID criteria clearly does not define the distinct disease ME.

The IOM does not recognize any further symptoms for diagnostic purposes other than 4/5 symptoms mentioned for a diagnosis. There is a lack of detail and extensive list of symptoms as suffered by those with ME as per the ICC.

Neither neurosensory, perceptual nor motor disturbances are included in the NAM/SEID guide.

Neither cardiac, respiratory, thermostatic instability issues are included in NAM/SEID guide

As of 2023 there are no US or International diagnostic codes for NAM/SEID criteria.

Patients who fit the criteria for ME may also fit the criteria for CFS (Holmes and Fukuda) and SEID, but the definitions are not synonymous nor interchangeable.

Summary: Fatigue Narrative
Minimum duration before diagnosis is 6 months. Delay in diagnosis symptoms must persist for at least 6 months before a diagnosis is made.

Hyde's The Nightingale Definition of Myalgic Encephalomyelitis (ME)

This Nightingale Research Foundation definition was presented at the IACFS/ME Conference Fort Lauderdale, Florida and Cornell University 2016.

The Nightingale Research Foundation created its own 2007 Definition of ME and updated it in 2016. In creating the Nightingale Definition, the Nightingale Research Foundation studied decades of clinical evidence, and followed up on the work of Dr. Melvin Ramsay (case descriptions published in 1981 and 1988), Dr. Elizabeth Dowsett, Dr. John Richardson, and others who closely studied ME patients and ME outbreaks over several decades.

Summary: an immunological and neurological disease

NICE Guidelines (UK) 2021

In 2018, NICE began appointing a committee of professionals and lay members to NICE guidelines review committee to rewrite the 2007 guidelines.  The new ME/CFS guidelines were published in October 2021, and include changes to the diagnostic criteria and recommended treatments.

Reasons for the update:

·       Out of 38 stakeholders, 32 wanted to update the guidelines, the Royal College of General Practitioners and 31 patient-representative bodies. 


·       The reanalysis of the data from the UK's 2011 £5 million PACE trial was hugely influential, with the full release of patient data in 2016 clearly showing no clinically significant improvements from graded exercise therapy (GET) or cognitive behavioural therapy (CBT, a psychological and behavioural treatment) which were the two key treatments in the 2007 NICE guidelines.


·       New scientific evidence was published, including the U.S. Institute of Medicine (NAM) report (2015), and the International Consensus Criteria (2011).


·       Post-exertional malaise was increasingly shown to be the hallmark symptom, not fatigue.


·       A petition by the UK's ME Association showed extremely widespread support for change by patients, carers, and the general public.


·       Patient surveys reported consistently that the GET and CBT treatments were ineffective and had caused widespread unexpected harm to the physical and mental health of a significant proportion of patients.


·       Since the publication of the previous guidelines, the Netherlands and United States had both abandoned the UK's prominent treatment approaches, and moved from using a underlying biopsychosocial model to a biomedical model of ME/CFS.


·       A number of doctors diagnosed with ME/CFS including Nina Muirhead became increasingly critical of the NICE guidelines and the NHS treatment offered to patients, and became involved in advocacy.

The NICE 2021 guideline covers diagnosing and managing myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome (ME/CFS) in children, young people and adults. It aims to improve awareness and understanding about ME/CFS and when to suspect it, so that people are diagnosed earlier. It includes recommendations on diagnosis, assessment and care planning, safeguarding, access to care and managing ME/CFS and its symptoms.”  
29 October 2021

Improvements to NICE 2021  
The new NICE Guideline (NG206) for Myalgic Encephalomyelitis (ME) WHO ICD G93.3 is a small but welcome step.  
The new NICE guideline recommends a route to earlier diagnosis for those with ME.  
The new guideline is only a small attempt to undo the damage done by inaction, ignorance, gaslighting and negligence since 2007.  While it is very far from ideal, and there is still a long way to go to provide appropriate guidance and policy development in Ireland, the removal of the most harmful treatment recommendations GET & CBT is a significant milestone on the road to proper recognition and treatment for ME.   
The new guidelines echo the longstanding views of many people with ME, their carers and families. 
The new NICE Guideline says that ME is a complex condition where there is no “one size fits all” approach to managing symptoms.


Problems NICE 2021  
Over emphasis on fatigue 
Use of PEM and not PENE as per ICC 
Guidelines are very much influenced by psych cabal in UK, the revision process and publication date were marred in controversy - there was a series of delays through the NICE guidelines review, including a three month "pause" in publication. 
Even well before the release of the new guidance, worrying evidence emerged about how GET, now removed, was already being repurposed by certain quarters (psych) in treating patients at clinics in the UK and the new label that is being used is Graded Activity Management (GAM).  
Even more worrying is the response by some stakeholders, i.e. the Royal Colleges, who, immediately following the publication of the new NICE Guidelines, indicated that they do not agree with the new guideline and will continue to promote their own brand of exercise and cbt treatments. 
Far from being the gold standard for guidelines for other countries, we would suggest that agencies developing guidelines in other parts of Europe should consider their own path and not blindly follow a UK organisation that has twice been taken to, or threatened with, a judicial review - by patients.  
A fiasco for what should have been an honest, open and significant process that could have removed the blight on the lives of people with ME caused by the last fourteen years of flawed guidelines being propped up by an out-of-date mentality in the UK.   
NICE Review 2018 -2021 and the intervening time 2007 - 2021 was a missed opportunity to evaluate new research, to document and recommend new treatments and practices, and to introduce new recommendations and guidance, effective treatments may well have become available during the fourteen years since 2007. Instead, the guidelines document of 2021 is only able to attempt to undo the damage done by inaction, ignorance, apathy and negligence during the past 14 years. 
More of the good and the bad here from Invest in ME Research's Statement 2021 


Summary: Overemphasis on fatigue and inappropriate therapies

Minimum duration before diagnosis is 3 months

NICE Guideline  [NG206] Published: 

"...two major errors are responsible for the present confusion surrounding the case definition, aetiology and diagnosis of M.E.  
First, there has been a failure to distinguish the syndrome from post-viral debility following Epstein-Barr mononucleosis, influenza and other common fevers.  Compared to M.E., these lack the dramatic effect of exercise upon muscle function, the multi-system involvement, diurnal variability of symptoms and prolonged relapsing course.  
Second, there has been a failure to recognize the unique epidemiological pattern of M.E."
- Dr. E.G. Dowsett-

As you can glean from the above, the research criteria used can vary enormously from country to country and medical discipline to medical discipline.

Despite the list of signs and symptoms and test exclusions in most of the above definitions, patients who conform to any of the CDC, Oxford, and Canadian CFS definitions may still have an undiagnosed major illness, certain of which are potentially treatable.

Unfortunately, the variety of criteria and labelling, as well as conflated labelling, being used worldwide to refer to ME, leads to so much confusion and controversy, the different criteria capture different kinds of patients and this in turn influences clinical research, the treatment options that are offered, and the various misperceptions of the illness by medics, welfare agencies and the general public. 

The muddied waters has prevented progress being made with regards to all aspects of ME to the detriment of the ME communities worldwide, the lack of consensus is the foremost cause of diluted and inconsistent research findings, which hinders progress, fosters skepticism, and wastes limited research funds.

The use of broad inclusion criteria has created a heterogeneous patient population within research. This has increased the risk of erroneous conclusions, misdiagnosis and incorrect treatment. It is the biggest roadblock to progress taking place with regards to many aspects of ME including the discovery of a diagnostic tool.

Despite the authors of the CFS and ME/CFS definitions repeatedly stating that they are defining a syndrome and not a specific disease, patient, physician, welfare and insurers have tended to treat this syndrome as a specific disease with, at times, a potentially specific treatment and a specific outcome. This has resulted in much confusion, and many physicians are now diagnosing CFS as though it were a specific illness. They either refer the patient to pharmaceutical, psychiatric, psychological, or social treatment or simply say: 'you have CFS and nothing can be done about it'. 
If in any person with CFS any major organ or system injury or disease is discovered, the patient is removed from the definition. 

Despite the quagmire of case definitions and the confusion that exists, ME and CFS are chronic illnesses. For too long most physicians have been managing ME and CFS, and chronically ill patients as they would acute short-term illnesses. Effective treatment of ME and CFS patients should depend upon precisely defining the organ and system pathologies and learning how to treat these patho-physiological conditions.

The various definitions of ‘CFS’ do not define Myalgic Encephalomyelitis (ME).  ME is an organic neurological disorder; the definitions of ‘CFS’ do not reflect this. 
The ‘CFS’ definitions are not watered down ME definitions, they are not definitions of ME at all.

Further Relevant Information

i. About Melvin Ramsay's textbook: - The Clinical Features of Myalgic Encephalomyelitis by Melvin Ramsay, M.D., 1986

ii. ME Epidemics here

iii. More about the Holmes Case Definition here

iv. More on the ICC and ICP here

v. De Paul University Symptom & Severity & PEM Questionnaires for Adults & Paediatrics: See all questionnaires here: De Paul Questionnaires  

vi. A comparison chart put together by shows the difference between ICC and SEID case definitions

vii. Summary of the major diagnostic criteria from 1988 onwards in OMF's Case Definition Chart

viii. A summary of clarifications and misconceptions re various case definitions from ME Action Demystifying the Diagnostic Criteria for ME

ME Advocates Ireland (MEAI) suggest adopting and using one of the best available case definitions and guidelines, i.e., the ME International Consensus Criteria and Primer for diagnosing and managing ME

Disclaimer: The information in this post is for general information purposes only. While we endeavour to keep the information up to date and correct, we make no representations or warranties of any kind, express or implied, about the completeness, accuracy, reliability, suitability or availability with respect to the post or the information, products, services, etc contained in the post for any purpose. Any reliance you place on such information is therefore strictly at your own risk. The suitability of any solution is totally dependent on the individual. It is strongly recommended to seek professional advice and assistance in some instances. 

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