Nijs, Jo, Vaes, Peter, De Meirleir, Kenny · Occupational therapy international · 2005 · DOI
Researchers created a simple questionnaire called the CFS-APQ to measure how much ME/CFS affects a patient's ability to do daily activities. They tested this questionnaire on hundreds of patients and found it works reliably—meaning patients give consistent answers when asked the same questions again—and it accurately reflects how sick someone is.
Having a validated, reliable tool to measure disease severity and activity limitation is essential for clinicians to track patient progress, compare treatment outcomes across studies, and capture the functional impact of ME/CFS. This questionnaire provides a standardized way to quantify one of the core features of ME/CFS that patients experience daily.
This study does not prove that the CFS-APQ can detect changes over time or in response to treatment (sensitivity was not examined). It does not establish whether the questionnaire is superior to other functional assessment tools, and the modest correlations with objective exercise capacity measures suggest the CFS-APQ captures subjective experience alongside, but not identical to, physiological limitation.
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
Nijs, Jo, Vaes, Peter, & De Meirleir, Kenny (2005). The Chronic Fatigue Syndrome Activities and Participation Questionnaire (CFS-APQ): an overview.. Occupational therapy international. https://doi.org/10.1002/oti.19
BibTeX
@article{mecfsatlas-nijs-2005-chronic-fatigue-2,
author = {Nijs, Jo and Vaes, Peter and De Meirleir, Kenny},
title = {The Chronic Fatigue Syndrome Activities and Participation Questionnaire (CFS-APQ): an overview.},
journal = {Occupational therapy international},
year = {2005},
doi = {10.1002/oti.19},
note = {PubMed: 16136868},
url = {https://www.mecfsatlas.com/evidence/nijs-2005-chronic-fatigue-2},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/nijs-2005-chronic-fatigue-2
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