Corbalán, Juan Antonio, Feltes, Gisela, Silva, Daniela et al. · Journal of clinical medicine · 2023 · DOI
Researchers developed a simple test called the Functional Limitation Index (FLI) to help doctors diagnose ME/CFS more quickly and objectively. The test uses measurements from exercise testing and breathing tests to identify how much a person's physical function is impaired. In their study, the FLI successfully distinguished ME/CFS patients from healthy people and athletes with high accuracy.
ME/CFS diagnosis currently relies on clinical criteria and exclusion of other conditions, creating diagnostic delays. An objective, physiologically-based parameter could accelerate diagnosis, reduce healthcare burden, and facilitate earlier intervention. This tool could improve care access for patients who often face delayed recognition of their condition.
This study does not prove that the FLI measures the underlying cause of ME/CFS or that abnormal FLI is specific to ME/CFS—it only shows association in this particular patient population. The study cannot establish whether FLI changes over time or predicts treatment response. Cross-sectional design prevents determining whether FLI abnormalities precede or follow ME/CFS onset.
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
Corbalán, Juan Antonio, Feltes, Gisela, Silva, Daniela, Gómez-Utrero, Eduardo, & Núñez-Gil, Iván J (2023). A Quick and Practical Approach to Secure a Chronic Fatigue Syndrome Diagnosis: The Novel Functional Limitation Index.. Journal of clinical medicine. https://doi.org/10.3390/jcm12227157
BibTeX
@article{mecfsatlas-corbaln-2023-quick-practical,
author = {Corbalán, Juan Antonio and Feltes, Gisela and Silva, Daniela and Gómez-Utrero, Eduardo and Núñez-Gil, Iván J},
title = {A Quick and Practical Approach to Secure a Chronic Fatigue Syndrome Diagnosis: The Novel Functional Limitation Index.},
journal = {Journal of clinical medicine},
year = {2023},
doi = {10.3390/jcm12227157},
note = {PubMed: 38002769},
url = {https://www.mecfsatlas.com/evidence/corbaln-2023-quick-practical},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/corbaln-2023-quick-practical
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