E3 PreliminaryModerate confidencePEM unclearMethods-PaperPeer-reviewedMachine draft
Psychometric properties of the Dutch Chronic Fatigue Syndrome--Activities and Participation Questionnaire (CFS-APQ).
Nijs, Jo, Vaes, Peter, McGregor, Neil et al. · Physical therapy · 2003
Quick Summary
Researchers tested a questionnaire designed to measure how ME/CFS affects daily activities and participation in normal life. The Dutch version of this questionnaire was given to people with ME/CFS, and the researchers found it reliably measured activity limitations and correlated well with patients' reports of pain and fatigue. This suggests the questionnaire is a useful tool for tracking how the disease impacts everyday functioning.
Why It Matters
Accurate measurement tools are essential for clinicians to objectively track how ME/CFS affects patients' daily functioning and for researchers to standardize outcomes in clinical trials. This validation of the CFS-APQ provides patients and healthcare providers with a reliable, disease-specific instrument specifically designed to assess activity limitations in ME/CFS rather than relying on generic disability measures.
Observed Findings
- CFS-APQ scores showed moderate convergent validity with pain (R=.51, P<.001) and fatigue (R=.50, P<.001) visual analog scales.
- 85.8% of patient-reported difficult activities matched content covered in the CFS-APQ (157 of 183 responses).
- Excellent test-retest reliability was demonstrated with intraclass correlation coefficients ≥.95 (P<.001) and Cronbach alpha of .94.
- 21 of 26 questions measured activity level; 5 measured participation level according to WHO ICIDH classification.
Inferred Conclusions
- The CFS-APQ demonstrates adequate convergent validity, content validity, and test-retest reliability for measuring activity limitations and participation restrictions in CFS patients.
- The questionnaire successfully captures the types of activities that patients report as difficult due to their condition.
- The CFS-APQ is structured in alignment with WHO disability classification frameworks, supporting its theoretical validity.
Remaining Questions
- Does the CFS-APQ demonstrate responsiveness—can it detect meaningful changes in activity limitations over time or in response to treatment?
- How does the CFS-APQ perform in patients across different severity levels and disease durations?
- What is the minimal clinically important difference (MCID) for the CFS-APQ to determine meaningful treatment effects?
What This Study Does Not Prove
This study does not establish whether the CFS-APQ is sensitive to changes over time (responsiveness) or whether it predicts treatment outcomes or disease progression. The moderate correlations with pain and fatigue (R=.50–.51) indicate the questionnaire measures related but distinct constructs, not that it explains the underlying biological mechanisms of ME/CFS.
Tags
Symptom:Cognitive DysfunctionPainFatigue
Method Flag:Weak Case DefinitionSmall Sample
Metadata
- PMID
- 12718710
- Review status
- Machine draft
- Evidence level
- Early hypothesis, preprint, editorial, or weak support
- Last updated
- 8 April 2026
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 →
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