McManimen, Stephanie L, Jason, Leonard A, Williams, Yolonda J · Fatigue : biomedicine, health & behavior · 2015 · DOI
This study looked at how ME/CFS is defined and diagnosed across different research centers. Researchers found that when different studies measure key symptoms like post-exertional malaise (feeling worse after activity), unrefreshing sleep, and brain fog, they get very different numbers—suggesting that either different patients are being studied, or researchers are asking questions in different ways. The study concluded that ME/CFS research needs more standardized, consistent methods for measuring symptoms so findings can be compared fairly.
This study addresses a fundamental problem in ME/CFS research: inconsistent diagnosis and measurement methods make it difficult to compare studies, replicate findings, and accurately understand how common the illness is. By highlighting these inconsistencies, the research advocates for better standardization that could lead to more reliable studies, better patient identification, and improved understanding of the disease.
This study does not prove what causes ME/CFS or validate any particular case definition as superior to others. It also does not establish that standardized methods will definitively solve all challenges in ME/CFS research, only that their absence contributes to current difficulties in comparing findings across studies.
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
McManimen, Stephanie L, Jason, Leonard A, & Williams, Yolonda J (2015). Variability in Symptoms Complicates Utility of Case Definitions.. Fatigue : biomedicine, health & behavior. https://doi.org/10.1080/21641846.2015.1041336
BibTeX
@article{mecfsatlas-mcmanimen-2015-variability-symptoms,
author = {McManimen, Stephanie L and Jason, Leonard A and Williams, Yolonda J},
title = {Variability in Symptoms Complicates Utility of Case Definitions.},
journal = {Fatigue : biomedicine, health & behavior},
year = {2015},
doi = {10.1080/21641846.2015.1041336},
note = {PubMed: 27088057},
url = {https://www.mecfsatlas.com/evidence/mcmanimen-2015-variability-symptoms},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/mcmanimen-2015-variability-symptoms
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