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Diagnostics 2016, 6(1), 10; doi:10.3390/diagnostics6010010
Abstract: Myalgic encephalomyelitis (ME), described in the medical literature since 1938, is characterized by distinctive muscular symptoms, neurological symptoms, and signs of circulatory impairment. The only mandatory feature of chronic fatigue syndrome (CFS), introduced in 1988 and redefined in 1994, is chronic fatigue, which should be accompanied by at least four or more out of eight “additional” symptoms. The use of the abstract, polythetic criteria of CFS, which define a heterogeneous patient population, and self-report has hampered both scientific progress and accurate diagnosis. To resolve the “diagnostic impasse” the Institute of Medicine proposes that a new clinical entity, systemic exercise intolerance disease (SEID), should replace the clinical entities ME and CFS. However, adopting SEID and its defining symptoms, does not resolve methodological and diagnostic issues. Firstly, a new diagnostic entity cannot replace two distinct, partially overlapping, clinical entities such as ME and CFS. Secondly, due to the nature of the diagnostic criteria, the employment of self-report, and the lack of criteria to exclude patients with other conditions, the SEID criteria seem to select an even more heterogeneous patient population, causing additional diagnostic confusion. This article discusses methodological and diagnostic issues related to SEID and proposes a methodological solution for the current “diagnostic impasse”.
2. Methodological Shortcomings of the Development Procedure of Systemic Exercise Intolerance Disease (SEID)
2.1. The Pre-Assumption that Myalgic Encephalomyelitis (ME) and Chronic Fatigue Syndrome (CFS) Denote “Similar Conditions” Is Invalid
- A unique form of muscle fatiguability: prolonged muscle weakness (and myalgia), lasting for days, even after a minor degree of physical effort (*1).
- Circulatory impairment, implicated by cold extremities and hypersensitivity to climatic change, but above all an ashen-grey facial pallor approximately 20 or 30 min before the patient complains of feeling ill.
- Cerebral dysfunction: impairment of memory and concentration and emotional lability, alterations of sleep rhythm (*2), vivid dreams (*2), episodic sweating and orthostatic tachycardia as cardinal features (the latter two not always present).
- Variability and fluctuation of both symptoms and physical findings over the day.
- A tendency to become chronic.
List 2. The diagnostic criteria of CFS .
- Severe chronic_fatigue for 6 or more consecutive months, that is not due to ongoing exertion or other medical conditions associated with fatigue and significantly interferes with daily activities and work,
- Accompanied by at least 4 or more of the following 8 symptoms:
- post-exertional malaise lasting more than 24 h (*1);
- unrefreshing sleep (*2);
- significant impairment of short-term memory or concentration;
- muscle pain;
- joint pain without swelling or redness;
- headaches of a new type, pattern, or severity;
- tender lymph nodes in the neck or armpit; and
- a sore throat that is frequent or recurring.
- chronic fatigue for 6 or more consecutive months;
- unrefreshing sleep;
- significant impairment of short-term memory or concentration;
- headaches of a new type, pattern, or severity; and
- a sore throat that is frequent or recurring.
- prolonged muscle weakness and muscle pain after minimal exertion;
- circulatory impairment, e.g., indicated by cold extremities, disturbed thermoregulation, low body temperature, and orthostatic tachycardia; and
- cognitive impairment and other symptoms indicating neurological dysfunction.
2.2. The Literature Analyzed by the Medicine (IOM) Committee Largely Relates to CFS Research
2.3. Consensus on “an Unclear Picture of the Symptoms” in a Heterogeneous Patient Group Does Not Guarantee a Good Solution
3. Diagnostic Shortcomings of the New Definition for “ME/CFS”: SEID
List 5. Proposed diagnostic criteria for SEID  (p. 6).
- a substantial reduction or impairment in the ability to engage in pre-illness levels of occupational, educational, social, or personal activities, that persists for more than 6 months and is accompanied by fatigue, which is often profound, is of new or definite onset (not lifelong), is not the result of ongoing excessive exertion, and is not substantially alleviated by rest;
- post-exertional malaise (*1); and
- unrefreshing sleep (*1)
- cognitive impairment (*1); or
- orthostatic intolerance
3.1. Neither ME nor CFS Is Covered by the Diagnostic Criteria of SEID
3.2. The Abstract and Ill-Defined Symptoms of SEID Cannot Be Assessed by Self-Report
3.3. The SEID Criteria Do Not Seem Reduce the Heterogeneity of the CFS Patient Population
3.4. The Definition of SEID Includes People with Other Conditions
4. Proposal for a Methodological Solution for the Current “Diagnostic Impasse”
4.1. Make a Clear Distinction between Patients Meeting the Diagnosis of ME or CFS
4.2. Symptoms Should Be Assessed Objectively If Feasible, Not Only by Self-Report
4.3. Take into Account Confounding Factors
4.4. Use Pattern Recognition Methods to Develop Empiric Definitions for ME, CFS-1 etc.
4.5. Diagnostic Labels Should Preferably Reflect the Clinical Picture
Conflicts of Interest
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