Moderator note: This post has been copied and following posts moved from this thread: Epidemiological and clinical factors associated with post-exertional malaise severity in patients with ME/CFS. Ghali et al. 2020 ____________________ PEM studies always catch my attention, especially ones that give a very good description of PEM in the introduction like this one does (it also uses an ICC cohort so all patients should by definition experience PEM).We sure need to know much, much more about PEM, how to identify and measure it, and what its relevance and implications really are. Yet reading through this study the main take-away is that we also need much, much better instruments to study PEM. 1) So they used the "PEM item from the standardized self-reported questionnaire of Center for Disease Control and Prevention Symptom Inventory (CDC SI) ." The reference  is this paper: https://pophealthmetrics.biomedcentral.com/articles/10.1186/1478-7954-3-8 which discusses the "CDC CFS Symptom Inventory" which mentions "unusual fatigue after exertion" (table 2) amongst a whole raft of other symptoms like sore throat and unrefreshing sleep. It seems to be primarily designed to ascertain whether you have CFS, not whether you have PEM. In fact, there's no actual mention of PEM in this referenced study so I don't understand what the "PEM item" in the present study is supposed to be, the whole questionnaire or just the item "unusual fatigue after exertion"? Looking at the scoring section, the latter - "unusual fatigue after exertion" - appears to be the most likely. If so, I'm sorry but "unusual fatigue after exertion" ain't no measure of PEM, not by itself anyway. Which the authors know very well going by how they describe PEM in the intro - so why use "unusual fatigue after exertion" as a measure of PEM (if I haven't misunderstood something)? 2) They only asked about the last month, and they only asked about frequency and severity of PEM. One month is surely too short a period to assess frequency - or anything much, really - and they completely fail to take into account the impact of pacing on frequency and severity of PEM despite the fact that they discuss patients using pacing to reduce PEM. 3) Importantly they fail to investigate how much/little exertion is needed to set off PEM. Or if there's a link between the level of overexertion and the severity of PEM. Not sure about this one. How do you decide whether your symptoms are those of an infection or of PEM? Do you simply have an infection or do you first have an infection which then sets off PEM? My personal sense is that infection and PEM are separate phenomena but that having an infection lowers PEM threshold, i.e. it takes less exertion to set off PEM when also having an infection. But it's hard to disentangle given that both infections and PEM present with flu-like malaise. The second of the two tools proposed by the IOM for PEM assessment is the De Paul symptom questionnaire*. I wonder why they didn't use that? Unlike the CDC SI self-reported questionnaire it was specifically designed for PEM though it still doesn't account for the impact of pacing, nor assesses the amount of exertion that leads to PEM. *https://www.leonardjason.com/wp-con...st-Exertional-Malaise-Questionnaire-DPEMQ.pdf And the CDC SI self-reported questionnaire can be downloaded here: https://www.cdc.gov/me-cfs/pdfs/symptom-inventory-questionnaire-508.pdf Is this something we could do better as a patient group? Many of the patient associations have good descriptive information on PEM but there don't seem to be any better scales than the two above to use in research. ETA: Fixed plural of phenomenon (= phenomena). I do hope that once we find a cure for ME that the brain fog at least is reversible. I would really like to have my former command of language back!