While many patients prefer "myalgic encephalomyelitis", which they believe better reflects the medical nature of the illness, there is resistance amongst some clinicians toward the use of myalgic encephalomyelitis on the grounds that the inflammation of the central nervous system (myelitis) implied by the term has not been demonstrated.A 2015 report from the Institute of Medicine recommended the illness be renamed "systemic exertion intolerance disease", (SEID), and suggested new diagnostic criteria, proposing post-exertional malaise, (PEM), impaired function, and sleep problems are core symptoms of ME/CFS. Additionally, they described cognitive impairment and orthostatic intolerance as distinguishing symptoms from other fatiguing illnesses. Economic impact
Reynolds et al. (2004) estimated that the illness caused about $20,000 per person with CFS in lost productivity, which totals to $9.1 billion per year in the United States. : 29  This is comparable to other chronic illnesses that extract some of the biggest medical and socioeconomic costs. Direct healthcare costs are estimated at between $9 and $14 billion annually in the US alone. A 2008 study calculated that the total annual cost burden of ME/CFS to society in the US was extensive, and could approach $24.0 billion. A 2017 estimate for the annual economic burden in the United Kingdom from ME/CFS was 3.3 billion pounds sterling. Awareness day
12 May is designated as ME/CFS International Awareness Day.
The 2015 definition by the National Academy of Medicine (then referred to as the "Institute of Medicine") is not a definition of exclusion (differential diagnosis is still required). "Diagnosis requires that the patient have the following three symptoms: 1) 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, and 2) post-exertional malaise* 3) Unrefreshing sleep*; At least one of the two following manifestations is also required: 1) Cognitive impairment* 2) Orthostatic intolerance" and notes that "*Frequency and severity of symptoms should be assessed. The diagnosis of ME/CFS should be questioned if patients do not have these symptoms at least half the time with moderate, substantial, or severe intensity. "Clinical practice guidelines are generally based on case descriptions, with the aim of improving diagnosis, management and treatment. An example is the ME/CFS guideline for the National Health Services in England and Wales, updated in 2021. Other guidance can be found at the New York Department of Health. Differential diagnosis
Certain medical conditions can cause chronic fatigue and must be ruled out before a diagnosis of CFS can be given.