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...
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 exacerbation of other symptoms, like muscle/joint pain, problems sleeping, headaches, cognitive dysfunction, sore throats, tender lymph nodes, and flu-like feelings (1). Furthermore, PEM can be delayed by hours to days relative to the triggering event and last hours, days, and even longer. In a recent survey (4) of almost 800 patients, over 90% endorsed the NAM’s description of PEM. In contrast, almost 70% felt that Dr. Jason’s conception of PEM, with its focus on fatigue (5) and lack of time-related characteristics, did not match their experiences. If PEM is conceived of as only post-exertional fatigue and chronological traits are not accounted for, study participants who do not actually experience PEM may be mis-classified as fitting the SEID criteria. The NAM report recognized that, currently, no short, accurate questionnaire exists for identifying PEM and strongly urged development of one.
1. Asprusten TT, Sulheim D, Fagermoen E, et al. Systemic exertion intolerance disease diagnostic criteria applied on an adolescent chronic fatigue syndrome cohort: evaluation of subgroup differences and prognostic utility. BMJ Paediatrics Open. 2018;2(1):e000233. doi:10.1136/bmjpo-2017-000233.
2. United States National Academy of Medicine Committee on the Diagnostic Criteria for Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome. Beyond myalgic encephalomyelitis/ chronic fatigue syndrome: redefining an illness. National Academies Press. https://www.nap.edu/read/19012/chapter/1. Published February 2015. Accessed April 2018.
3. Chu L, Valencia IJ, Montoya JG. Differences of opinion on systemic exercise intolerance disease are not ‘mistakes’: a rejoinder to Jason Sunnquist, Gleason and Fox, Fatigue: Biomedicine, Health & Behavior. 2017; 5(4):239-244. doi: 10.1080/21641846.2017.1362750.
4. United States National Institutes of Health National Institute of Neurologic Disorders and Stroke Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome Common Data Elements Project. Public comments, p. 87-89 and p.128-142. US National Institutes of Health. https://www.nih.gov/sites/default/files/research-training/initiatives/me.... Published March 2018. Accessed April 2018.
5. Jason LA, Sunnquist M, Kot B, et al. Unintended Consequences of not Specifying Exclusionary Illnesses for Systemic Exertion Intolerance Disease. Kjaer A, ed. Diagnostics. 2015;5(2):272-286. doi:10.3390/diagnostics5020272.