Lim, Eun-Jin, Kang, Eun-Bum, Jang, Eun-Su et al. · Journal of clinical medicine · 2020 · DOI
Researchers reviewed studies testing a two-day exercise test (called CPET) that might help diagnose ME/CFS by measuring how the body performs differently on day two compared to day one. In ME/CFS patients, performance dropped on day two, while it improved in healthy people—suggesting this test could objectively measure the characteristic crash (postexertional malaise) that follows exertion in ME/CFS. The test showed promise, but more large-scale studies are needed before it can be used clinically.
ME/CFS lacks objective diagnostic biomarkers, making diagnosis difficult and delaying patient care. If validated, the two-day CPET could provide physicians with an objective test to confirm ME/CFS and document PEM—the hallmark symptom—potentially improving diagnostic accuracy and standardizing clinical assessment across different medical centers.
This meta-analysis does not establish the two-day CPET as a validated diagnostic tool; it demonstrates only proof-of-concept potential. The study does not prove the test can distinguish ME/CFS from other fatiguing illnesses like depression or other post-viral conditions, nor does it confirm whether observed declines are specific to PEM versus general deconditioning or other mechanisms.
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
Lim, Eun-Jin, Kang, Eun-Bum, Jang, Eun-Su, & Son, Chang-Gue (2020). The Prospects of the Two-Day Cardiopulmonary Exercise Test (CPET) in ME/CFS Patients: A Meta-Analysis.. Journal of clinical medicine. https://doi.org/10.3390/jcm9124040
BibTeX
@article{mecfsatlas-lim-2020-prospects-two,
author = {Lim, Eun-Jin and Kang, Eun-Bum and Jang, Eun-Su and Son, Chang-Gue},
title = {The Prospects of the Two-Day Cardiopulmonary Exercise Test (CPET) in ME/CFS Patients: A Meta-Analysis.},
journal = {Journal of clinical medicine},
year = {2020},
doi = {10.3390/jcm9124040},
note = {PubMed: 33327624},
url = {https://www.mecfsatlas.com/evidence/lim-2020-prospects-two},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/lim-2020-prospects-two
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