Canadian Consensus Criteria

The Canadian consensus criteria (CCC) or the Canadian working definition are a proposed clinical criteria for ME/CFS, published in 2003, and frequently used as a case definition in research. The Canadian definition is a strictest diagnostic criteria, selecting a smaller group of patients than the Fukuda criteria and a more severely impaired population. Adults are diagnosed after a minimum of six months of illness and children after a minimum of three months.

Definition
To be included, the symptoms must have begun or have been significantly altered after the onset of this illness. It is unlikely that a patient will suffer from all symptoms in criteria 5 & 6. The disturbances tend to form symptom clusters that may fluctuate and change over time. Children often have numerous prominent symptoms but their order of severity tends to vary from day to day.

(*) There is a small number of patients who have no pain or sleep dysfunction, but no other diagnosis fits except ME/CFS. A diagnosis of ME/CFS can be entertained when this group has an infectious illness type onset.

(**) Some patients have been unhealthy for other reasons prior to the onset of ME/ CFS and lack detectable triggers at onset or have more gradual or insidious onset.

1 "Overload" refers to hypersensitivities to stimuli that have changed from pre-illness status.

2 "Crash" refers to a temporary period of immobilizing physical and /or cognitive fatigue.

Idiopathic chronic fatigue
People with chronic fatigue (lasting at least six months) but not meeting the criteria for ME/CFS should be diagnosed with idiopathic chronic fatigue instead.

Authors
Bruce Carruthers, Anil Kumar Jain, Kenny de Meirleir, Daniel Peterson, Nancy Klimas, A Martin Lerner, Alison Bested, Pierre Flor-Henry, Pradip Joshi, A C Peter Powles, Jeffrey Sherkey, Marjorie van de Sande

Generally accepted criteria for diagnosis

 * Canadian consensus criteria (CCC). A diagnosis of moderate and severe forms of ME/CFS are accurately made using these criteria. Adults can be diagnosed at 6 months while pediatric cases are diagnosed at three months.
 * International consensus criteria (ICC). These criteria will accurately diagnose myalgic encephalomyelitis (ME). There is no requirement that the individual have symptoms for a specified period of time for diagnosis, as opposed to CCC, Fukuda, and SEID, which all require 6 months in adults.
 * CDC Myalgic Encephalomyelitis/Chronic Fatigue Syndrome 2017 diagnostic criteria - originally known as the Systemic exertion intolerance disease (SEID) criteria ME/CFS (SEID) is accurately diagnosed when the core symptoms are met. The Institute of Medicine report as a whole is a comprehensive review of the medical literature available at time of publication (2015). Adults can be diagnosed at 6 months while pediatric cases are diagnosed at three months.

Learn more

 * A Clinical Case Definition and Guidelines for Medical Practitioners - An Overview of the Canadian Consensus Document (the above 7 criteria are listed on page 2 of this document).
 * Canadian Consensus Report - Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Clinical Working Case Definition, Diagnostic and Treatment Protocols (full version of the Canadian consensus criteria).
 * An Overview of the Canadian Consensus Document in French - Encéphalomyélite myalgique/syndrome de fatigue chronique: Définition clinique et lignes directrices à l’intention des médecins, Abrégé du Consensus canadien