I think epidemiology is by far and away the number one research priority for ME/CFS however we need to understand what can be achieved, what needs to be achieved and at what cost.
Large scale random sampling of whole populations which involves detailed medical examination of individuals, is both massively expensive and difficult to achieve.
A bit like the apocryphal tourist who stops to ask the way to Dublin and receives the reply "it'd be better not to start from here" we can wish to have epidemiology based solely on our preferred criteria but the reality is that 10s, maybe 100s of 1,000s of patients have a diagnosis that uses older/different criteria. Not only is it impractical to work wholly from 'as new', it is important to understand what those past criteria represent, what patient population is captured by them and how that patient population relates to a that exclusively captured by a preferred criteria.
At present we know very little about the patient population that has been diagnosed with criteria that are likely to capture those who we might agree are 'genuine' ME/CFS patients. Age, age at onset, pattern of illness, level of disability, socioeconomic background and situation, geographic spread - even the much touted gender imbalance is uncertain. Irrespective of criteria fit, all these people who have a diagnosis are in need of responsive health and social services, and at the very least commissioners of those services need good data in order to provide for that need.
If we take the UK as a basis for what might be a way forward -it has largely integrated health system with extensive data - it is possible to describe a potentially useful epidemiological study. The aim would be to enumerate the number of people who have been given formal or informal (GP only) diagnosis of PVS, ME, CFS etc by whatever criteria, and to describe that population by demographics, diagnostic criteria applied, service use etc.
Once this global population had been properly described it would be possible to test, by sampling across demographics, how a preferred diagnosed criteria matched or mismatched historical diagnoses. This would then usefully inform biomedical research as to the significance, or otherwise, of individual patient characteristics. It maybe that the pathology of ME/CFS can be distinguished from other similarly presenting pathologies by the use of symptom based criteria alone, but it might also be the case that age, or gender or ethnicity or environmental exposure or something else, are of equal or even greater significance.
PEM, for example may be the great divide it currently appears to be, or PEM may pale into statistical insignificance when compared to some wholly unexpected characteristic. Without pathophysisiological findings we need to remain sceptical of the usefulness of case criteria to precisely circumscribe the commonality of underlying disease in the patient population. For now the epidemiology of ME/CFS needs to be fairly broadly cast.
Edit to add missing words
I take your points. However, in my view, we are not starting from 0 with our understanding of this disease. We have good definitions of ME/CFS in the Canadian Consensus Criteria, and the International Consensus Criteria.
The Canadian Consensus Criteria (CCC) with 11 world experts, is superior to the Fukuda definition. The Fukuda definition allows more psychiatric signs and symptoms, and PEM is optional, whereas with the CCC, PEM is required, and this criteria emphasizes more physical disability.
I also note that the 2015 Institute of Medicine, now the National Academy of Medicine criteria requires PEM. This body recognized PEM as the hallmark of ME/CFS:
https://www.nap.edu/resource/19012/MECFS_ProposedDiagnosticCriteria.jpg
(The International Consensus Criteria is also superior to Fukuda; I will not comment further here on that criteria:
https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2796.2011.02428.x)
The Canadian Consensus Criteria, pages 9 and 10 advises: " Based on the consensus panels' collective extensive clinical experience diagnosing and/or treating more than twenty thousand (20,000) ME/CFS patients, a working clinical case definition, that encompassed the pattern of positive signs and symptoms of ME/CFS was developed."
https://www.mefmaction.com/images/stories/Medical/ME-CFS-Consensus-Document.pdf
From the study in large bold print below:
"The findings suggest that both the Canadian and Fukuda et al. case definitions select individuals who are statistically significantly different from psychiatric controls with chronic fatigue, with the Canadian criteria selecting cases with less psychiatric co-morbidity, more physical functional impairment, and more fatigue/weakness, neuropsychiatric, and neurological symptoms."
Comparing the Fukuda et al. Criteria and the Canadian Case Definition for Chronic Fatigue Syndrome
Leonard A. Jason
,
Susan R. Torres-Harding
,
Amber Jurgens
&
Jena Helgerson
Pages 37-52 | Received 07 Jun 2003, Accepted 25 Sep 2003, Published online: 04 Dec 2011
https://www.tandfonline.com/doi/abs/10.1300/J092v12n01_03
Authors, Mary Dimmock, and Matthew Lazall-Fairman's document Thirty Years of Disdain, page 154 contains a summary comparison of the various ME/CFS criteria:
https://www.dropbox.com/s/bycueauxmh49z4l/Thirty Years of Disdain - Background.pdf?dl=0
One can see from the chart in the above Dimmock, and Lazall-Fairman document that over time, signs and symptoms have been excluded or included in various criteria. The Holmes criteria in 1988, has more signs of infection than the Fukuda definition which was published in 1994.
For decades our community has been saddled with overly broad criteria, which has blurred the outlines of this illness to such an extent it has become indistinct from burn out, depression, and just everyday fatigue etc. In my opinion we must not accept the continued reliance on case definitions that assign pwME to such diagnoses, nor accept token amounts of research funding.
