Definitions of myalgic encephalomyelitis and chronic fatigue syndrome

Over the course of three decades, many definitions or case criteria have been developed to diagnose either myalgic encephalomyelitis (ME), chronic fatigue syndrome (CFS), or Systemic Exertion Intolerance Disease (SEID) which is an ME/CFS criteria. Some of these definitions or criteria are meant only to be diagnostic, i.e., used in a clinical setting to aid in diagnosis and some are meant to be used both in a clinical and research setting.

Each of these criteria and case definitions have been considered lacking in complete reliability and accuracy. Another change in the definition is assumed when medical research uncovers more of the pathophysiology of this illness.

ME

 * 1986 Ramsay definition
 * 2007 Nightingale definition
 * 2011 International Consensus Criteria (ICC)
 * 2014 London criteria

The International Consensus Criteria is currently used in some research and by few clinicians in some countries. Ramsay definition, Nightingale definition and London criteria are currently not in use.

CFS

 * 1988 CDC case definition ("Holmes criteria")
 * 1991 Oxford criteria*
 * 1994 CDC case definition ("Fukuda criteria")* (CDC-1994)
 * 2005 CDC case definition ("Reeves criteria")*

The Holmes criteria is currently not in use. The Oxford criteria has been very recently retired but was heavily used in the UK by researchers and some clinicians. The Fukuda criteria is used in research by several countries including the US and sometimes in the UK. Reeves criteria is currently being used in the NIH Post-Infectious ME/CFS Study but overall it is not in use.

Combined (ME/CFS)

 * 2021, NICE ME/CFS diagnostic criteria
 * 2003 Canadian Consensus Criteria (CCC)
 * 2007 NICE CFS/ME guidelines*

The Canadian Consensus Criteria is sometimes used by clinicians and for research in many countries but has not been officially adopted by most countries including the US. NICE guidelines are used by clinicians in the UK.

Note: ME/CFS (or CFS/ME in parts of Europe) is the acronym now used in the US, UK, and some other countries.

'SEID'

 * 2015 Institute of Medicine (IOM) diagnostic criteria
 * The name "Systemic Exertion Intolerance Disease" (SEID) was proposed in conjunction with this criteria, but was not adopted.
 * Currently used for by the CDC for ME/CFS diagnosis

The IOM criteria is an ME/CFS criteria proposed for use in the US in clinical settings. The NIH Post-Infectious ME/CFS Study is using this criteria along with three other criteria.

The Centers for Disease Control and Prevention (CDC) outlines the IOM diagnostic criteria on their ME/CFS page IOM 2015 Diagnostic Criteria.

Note on Definition flaws
Definitions with a asterisk (*) are considered to be by most ME/CFS patients, many ME/CFS patients groups, and several ME/CFS researchers as being seriously flawed in that these criteria capture individuals suffering from chronic fatigue and not chronic fatigue syndrome, myalgic encephalomyelitis or Systemic Exertion Intolerance Disease.

Comparison

 * 2001, A definition-based analysis of symptoms in a large cohort of patients with chronic fatigue syndrome - (Full text)
 * 2003, Variability in diagnostic criteria for chronic fatigue syndrome may result in substantial differences in patterns of symptoms and disability - (Full text)
 * 2012, Contrasting case definitions for chronic fatigue syndrome, Myalgic Encephalomyelitis/chronic fatigue syndrome and myalgic encephalomyelitis - (Full text)
 * 2015, Accurate diagnosis of myalgic encephalomyelitis and chronic fatigue syndrome based upon objective test methods for characteristic symptoms - (Full text)
 * 2015, Chronic Fatigue Syndrome and Myalgic Encephalomyelitis: Toward An Empirical Case Definition - Case Definition Comparison - Graph 1 - (Full text)
 * 2016, Chronic Fatigue Syndrome versus Systemic Exertion Intolerance Disease - (Full text)
 * 2017, Patients diagnosed with Myalgic encephalomyelitis/chronic fatigue syndrome also fit systemic exertion intolerance disease criteria (Lily Chu), (Jane Norris), (Ian Valencia) & (Jose Montoya) - (Full text)
 * 2017, A Comparison of Case Definitions for Myalgic Encephalomyelitis and Chronic Fatigue Syndrome - (Full text)
 * 2017, How have selection bias and disease misclassification undermined the validity of myalgic encephalomyelitis/chronic fatigue syndrome studies? - (Full text)

Narrowest and broadest diagnostic criteria
The retired Oxford criteria for CFS selected the highest number of patients as having CFS, and the Canadian definition of ME/CFS selects the smallest number of patients, leading to radically different results in research. Nacul et al. (2017) stated:
 * "For every 15 patients selected under Oxford criteria, 14 will be false positives when compared to Canadian Consensus Criteria. The Pace trial and FINE trial used Oxford criteria."
 * "When studies using the broad Oxford criteria (Sharpe et al., 1991) were excluded, a virtual disappearance of effect for graded exercise therapy (GET), cognitive behaviour therapy (CBT) and other psychological therapies recommended by the NICE guidelines (National Institute for Health and Care Excellence (NICE), 2007) was revealed."

Learn more

 * CFS vs SEID - Tandfonline The Four-symptom criteria is noted.
 * Chronic Fatigue Syndrome and Myalgic Encephalomyelitis: Toward An Empirical Case Definition See: Graph - 1
 * Excluding Factors: Jason Critiques the IOM Definition for ME/CFS - Health Rising - Cort Johnson The Four-symptom criteria is noted.