Twisk, Frank · Diagnostics (Basel, Switzerland) · 2018 · DOI
This paper proposes a clear, practical definition of ME (myalgic encephalomyelitis) to help doctors reliably identify and study the condition. The authors argue that ME is a distinct multi-system illness characterized by severe muscle exhaustion after minimal activity, neurological symptoms (like brain fog and autonomic problems), and a pattern of symptom fluctuation and relapse over months or years. Having a precise definition is essential so researchers can study the right patients and develop effective treatments.
Clear diagnostic criteria are fundamental to ME/CFS research—without them, studies may inadvertently enroll heterogeneous patient populations, making it impossible to develop targeted therapies. This paper addresses the critical problem that ME has been conflated with the broader, less-specific CFS label, potentially obscuring the disease's true biology and slowing therapeutic progress.
This is a definitional/conceptual paper, not a prospective clinical validation study, so it does not prove that the proposed criteria will reliably distinguish ME from other conditions in practice. The paper does not establish the biological mechanisms underlying ME, nor does it validate these criteria against biomarkers or imaging findings. It is a framework proposal rather than empirical evidence of diagnostic accuracy.
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
Twisk, Frank (2018). Myalgic Encephalomyelitis (ME) or What? An Operational Definition.. Diagnostics (Basel, Switzerland). https://doi.org/10.3390/diagnostics8030064
BibTeX
@article{mecfsatlas-twisk-2018-myalgic-encephalomyelitis,
author = {Twisk, Frank},
title = {Myalgic Encephalomyelitis (ME) or What? An Operational Definition.},
journal = {Diagnostics (Basel, Switzerland)},
year = {2018},
doi = {10.3390/diagnostics8030064},
note = {PubMed: 30205585},
url = {https://www.mecfsatlas.com/evidence/twisk-2018-myalgic-encephalomyelitis},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/twisk-2018-myalgic-encephalomyelitis
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