| NB: When considering information concerning groups of people with ME/CFS and those with long COVID, it is important to remember that ME/CFS is a symptom-based clinical diagnosis not a mechanistic one. It is clear there is a high degree of shared pathophysiology between ME/CFS and long COVID, and the two diagnostic labels are not mutually exclusive. Importantly, some individuals with long COVID meet ME/CFS diagnostic criteria or have a dual diagnosis. |
Professor Leonard Jason and colleagues have published a study comparing 55 people who developed ME/CFS following infectious mononucleosis (infection with Epstein-Barr Virus, which occurred prior to the COVID-19 pandemic) with 55 people who had developed long COVID after a sars-CoV-2 infection.
Notably, information on those with ME/CFS came from a previously established project, also led by Prof. Jason, and enabled the researchers to group participants into “moderate ME/CFS” if they only met one diagnostic criteria, or “severe ME/CFS” if they met more than one.
The criteria used in the study were:
- Fukuda criteria for CFS (does not require the presence of post-exertional malaise for a diagnosis to be made).
- Canadian Consensus Criteria (CCC) for ME/CFS.
- Institute of Medicine (IoM) criteria for ME/CFS.
It is essential to note that this method of grouping people into ‘moderate’ or ‘severe’ ME/CFS is not the same as categories used elsewhere, such as those in the 2021 guidelines for the diagnosis and management of the disease.
The researchers found that, in general, those with long COVID had:
- A lower symptom burden than those with ‘severe’ ME/CFS
- A higher symptom burden than those with ‘moderate’ ME/CFS
It is important to recognise that most cases of ‘moderate’ ME/CFS, only met the Fukuda criteria for CFS, while the ‘severe’ ME/CFS group always met the Fukuda criteria and either the CCC or the IoM criteria.
Additionally, this study did not consider whether those with long COVID also met ME/CFS diagnostic criteria. it is possible that symptom burden would be different between those who only have long COVID but do not meet ME/CFS criteria, and those with long COVID who do, and indeed in this study, vary again depending on the ME/CFS criteria used.
The researchers cite the following limitations of their study:
- Relatively small sample size.
- Only three months of symptoms were required for a diagnosis of long COVID compared with 6 months for those with ME/CFS, something the team state means limits knowledge around the stability of long COVID cases in this study.
Conclusions made in the paper highlight that “future studies will be directed at examining immunologic or metabolomic commonalities and differences between ME/CFS and long COVID.”
