The Chronic Fatigue Syndrome Activities and Participation Questionnaire (CFS-APQ): an overview.
Nijs, Jo, Vaes, Peter, De Meirleir, Kenny · Occupational therapy international · 2005 · DOI
Quick Summary
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.
Why It Matters
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.
Observed Findings
Test-retest reliability coefficient was 0.95 across 34 participants, indicating highly consistent responses.
Internal consistency (Cronbach α) ranged from 0.87 to 0.94 across two independent samples.
85.8% of 183 activities patients reported as difficult matched the content of the CFS-APQ, supporting face validity.
CFS-APQ scores correlated with behavioural performance assessments (r=0.29-0.55) and exercise capacity parameters (r=0.26-0.39).
CFS-APQ correlated with pain (r=0.51) and fatigue (r=0.50) visual analogue scales.
Inferred Conclusions
The CFS-APQ is a reliable and internally consistent instrument for measuring activity limitation in ME/CFS patients.
The questionnaire demonstrates validity across multiple domains including self-reported functional limitation, objective performance, and symptom severity.
The CFS-APQ can be used as a clinical measure of disease severity in ME/CFS populations.
Future research should examine the sensitivity of the tool to detect clinically meaningful changes over time.
Remaining Questions
Does the CFS-APQ detect meaningful changes in function following treatment or disease progression (sensitivity/responsiveness)?
What This Study Does Not Prove
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.
Tags
Symptom:Post-Exertional MalaisePainFatigue
Method Flag:Weak Case DefinitionSmall SampleExploratory Only
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 →