Dr Nuno Sepúlveda and Dr Francisco Westermeier – researchers who have previously worked on projects funded by ME Research UK, have written a letter to the editor of the Journal of Infection in response to a systematic review – a type of study that uses repeatable methods to search for, select, and combine all available evidence to answer a specific research question, which concluded that 51% of people with long COVID met ME/CFS diagnostic criteria.
In their letter, Sepúlveda and Westemeier highlight several potential methodological issues with the systematic review, notably that the 13 included articles do not meet conditions specified by the European Network on Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (EUROMENE) which state that:
- Included studies should use data collected for the purposes of answering the specific research question at hand – primary data.
- Studies conducted in biased samples – samples that have been collected in such a way that means some members of the intended population are more or less likely to have been included than others, should be excluded.
- Studies included in the review should not use information based on self-reported ME/CFS diagnosis.
- Studies using inappropriate case definitions – such as “CFS-like illness”, should be excluded from the review.
- Duplicate reports – studies which use the same dataset, should also be excluded. Rather, where data from multiple studies overlap, the study with the largest number of participants should be selected for inclusion.
Sepúlveda and Westemeier conclude that implication of these methodological issues is that the finding – that approximately 50% of people with long COVID meet ME/CFS criteria, is likely to be an overestimation that can be explained by “biased samples” recruited from long COVID support groups. It is however important to note that, although relevant to consider here, the conditions set out by EROMENE were developed for the purposes of a different systematic review and not specifically published as a methodological tool to be used in future research studies.
Interestingly, the methodological issues highlighted in the letter to the editor by Sepúlveda and Westemeier are reminiscent of those recently identified in a paper by Mark Vink, which also re-examined a systematic review and confirmed the conclusion by NICE that CBT is not an effective treatment for ME/CFS. Both the letter by Sepúlveda and Westemeier, and the paper by Mark Vink act as a reminder that all published research must be interpreted with a critical eye.
This is why ME Research UK aims to provide our supporters with impartial critical summaries of research relating to ME/CFS which highlight findings in light of any study limitations.
Steps can also be taken at a study development phase to help to ensure that research is based on sound science from the start. This is why ME Research UK requires all research grant applications to go through a rigorous peer review process prior to any funding being awarded.
