Scartozzi, Samantha, Sunnquist, Madison, Jason, Leonard A · Fatigue : biomedicine, health & behavior · 2019 · DOI
ME/CFS diagnoses require doctors to confirm that patients have a significant drop in their ability to function compared to before they got sick. However, there's no clear agreement on how much of a drop counts as 'significant.' This study looked at over 1,000 people with ME/CFS to see whether this requirement actually helps doctors identify who has the illness. The researchers found that when diagnostic criteria clearly describe which symptoms to look for and how severe they should be, the 'significant drop in functioning' requirement may not be necessary.
This research addresses a fundamental problem in ME/CFS diagnosis: inconsistent application of diagnostic criteria across research studies undermines scientific validity and patient recognition. By clarifying whether the 'substantial reduction in functioning' requirement is actually necessary, this work could lead to more standardized, efficient diagnostic approaches that benefit both clinical care and research comparability.
This study does not establish causation or prove that the substantial reduction criterion should be eliminated from all case definitions. It also does not demonstrate optimal case definition design overall—only that symptom specificity may reduce dependence on the functioning criterion. The convenience sampling approach means findings may not represent the full ME/CFS population.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Scartozzi, Samantha, Sunnquist, Madison, & Jason, Leonard A (2019). Myalgic encephalomyelitis and chronic fatigue syndrome case definitions: effects of requiring a substantial reduction in functioning.. Fatigue : biomedicine, health & behavior. https://doi.org/10.1080/21641846.2019.1600825
BibTeX
@article{mecfsatlas-scartozzi-2019-myalgic-encephalomyelitis,
author = {Scartozzi, Samantha and Sunnquist, Madison and Jason, Leonard A},
title = {Myalgic encephalomyelitis and chronic fatigue syndrome case definitions: effects of requiring a substantial reduction in functioning.},
journal = {Fatigue : biomedicine, health & behavior},
year = {2019},
doi = {10.1080/21641846.2019.1600825},
note = {PubMed: 31788347},
url = {https://www.mecfsatlas.com/evidence/scartozzi-2019-myalgic-encephalomyelitis},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-29. https://www.mecfsatlas.com/evidence/scartozzi-2019-myalgic-encephalomyelitis
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