Review of case definitions for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)

Abstract

Background: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating disease with unknown causes. From the perspectives on the etiology and pathophysiology, ME/CFS has been labeled differently, which influenced changes in case definitions and terminologies. This review sought to feature aspects of the history, developments, and differential symptoms in the case definitions. Methods: A search was conducted through PubMed published to February 2020 using the following search keywords: case definition AND chronic fatigue syndrome [MeSH Terms]. All reference lists of the included studies were checked. Of the included studies, the number of citations and the visibility in the literatures of the definitions were considered for comparisons of the criteria. Results: Since the first 'ME' case definition was developed in 1986, 25 case definitions/diagnostic criteria were created based on three conceptual factors (etiology, pathophysiology, and exclusionary disorders). These factors can be categorized into four categories (ME, ME/CFS, CFS, and SEID) and broadly characterized according to primary disorder (ME-viral, CFS-unknown, ME/CFS-inflammatory, SEID-multisystemic), compulsory symptoms (ME and ME/ CFS-neuroinflammatory, CFS and SEID-fatigue and/or malaise), and required conditions (ME-infective agent, ME/ CFS, CFS, SEID-symptoms associated with fatigue, e.g., duration of illness). ME and ME/CFS widely cover all symptom categories, while CFS mainly covers neurologic and neurocognitive symptoms. Fatigue, cognitive impairment, PEM, sleep disorder, and orthostatic intolerance were the overlapping symptoms of the 4 categories, which were included as SEID criteria. Conclusions: This study comprehensively described the journey of the development of case definitions and compared the symptom criteria. This review provides broader insights and explanations to understand the complexity of ME/CFS for clinicians and researchers.

The evidence base for physiotherapy in myalgic encephalomyelitis/chronic fatigue syndrome when considering post-exertional malaise: a systematic review and narrative synthesis

“…The most commonly used are “Myalgic Encephalomyelitis”, “Chronic Fatigue Syndrome”, and the umbrella-term ME/CFS. Whether PEM is a cardinal feature of ME/CFS, and accordingly whether ME and CFS are distinct clinical entities, has been debated for almost two decades [ 30 ]. For purposes of clarity, in this review, the label “ME” will be used when PEM is a cardinal feature and the other core symptoms are present as well [ 31 ].…”

Diagnostic and Pharmacological Potency of Creatine in Post-Viral Fatigue Syndrome

“…Although some CFS/ME cases are not preceded by a viral infection [2], all conditions share clinical features that allow for a mutual medical/scientific exploration. Mainly characterized by a prolonged severe post-exercise malaise, an impairment in various cognitive functions, non-inflammatory myalgia and joint pain, and unrefreshing sleep, PVFS has an unknown cause, no pathognomonic diagnostic criteria, and no approved medical treatment (for a detailed review see [3][4][5]). Various viral infections have often been reported before the first appearance of PVFS, including Epstein-Barr virus, cytomegalovirus, coxsackieviruses, and coronaviruses, and the onset might be sudden or gradual [6].…”

ME (Ramsay) and ME-International Case Criteria (ME-ICC): two distinct clinical entities

“…The review of the differences and similarities in the different case definitions for myalgic encephalomyelitis (ME)/chronic fatigue syndrome (CFS) by Lim and Son [ 1 ] deserves appreciation. Based on their analysis the authors acknowledge the “distinct view of ME and CFS” [ 2 ] and recognize four categories of case definitions: ME, ME/CFS, CFS [ 3 ] and Systemic Exertion Intolerance Disorder (SEID) [ 4 ].…”

“…Indeed these labels reflect very different case definitions [ 5 ]. According to Lim and Son [ 1 ] the first category comprises two ‘ME’ case definitions: ME (Ramsay) [ 6 ] and ME according to the International Case Criteria (ME-ICC) [ 7 ]. However as can be deduced from Table 2 [ 1 ], ME [ 6 ] and ME-ICC [ 7 ] are two distinct clinical entities [ 8 ].…”

“…Finally, it is important to note that, in contrast with Table 2 [ 1 ], ME [ 6 ] is often but not always triggered by an infection and that ME requires at least four symptoms: muscle fatigability/prolonged post-exertional muscle weakness and three neurological symptoms indicative of cognitive, autonomic and sensory dysfunction.…”