eLetters

11 e-Letters

  • Post-exertional fatigue is not equivalent to post-exertional malaise

    To the Editor: Dr. Wyller and his research team are to be commended for their efforts to validate the Systemic Exertion Intolerance Disease (SEID) criteria (1). As a co-author of the US National Academy of Medicine (NAM, the new name for the Institute of Medicine) report (2), I encourage testing of it and have written about how, without a diagnostic gold standard test, case definitions could be judged by whether they help clinicians and researchers prevent, understand, treat, or predict the course of a medical condition (3). There are a two concerns I have about this study.

    First, Wyller et al. noted that 39% of their subjects (45 out of 115) qualified for the SEID criteria while 61% did not. What were the most common reasons for why subjects did not qualify for the SEID criteria? Were these primarily qualitative reasons, where the SEID group were more likely to suffer from a particular symptom at all, or a quantitative one, where, for example, both groups experienced the same symptoms but the former experienced them at a higher intensity? Understanding these differences would lend further context to their results and assist in future refinement of any ME/CFS criteria.

    Second, although the authors acknowledge lack of a PEM-specific item in their study, I wish to re-emphasize that post-exertional fatigue is not equivalent to post-exertional malaise. As described in the NAM report, PEM is not only increased fatigue following activity but also involves exa...

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