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Quantifying the Degree of Fatigue in People Reporting Symptoms of Post-COVID-19 Syndrome: Results from a Rasch Analysis. — ME/CFS Atlas

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Quantifying the Degree of Fatigue in People Reporting Symptoms of Post-COVID-19 Syndrome: Results from a Rasch Analysis.

Mayo, Nancy, Brouillette, Marie-Josée, Fellows, Lesley K et al. · Physiotherapy Canada. Physiotherapie Canada · 2025 · DOI

Quick Summary

Researchers in this study developed and tested a new questionnaire to measure fatigue severity in people with post-COVID-19 syndrome. The measure, called the PCS Fatigue Severity Measure V1, performed well in their analysis of 414 participants—it correlated strongly with other fatigue measures and distinguished between people still working and those on sick leave. However, this is early-stage research in a single Canadian cohort, and the authors note that further testing in other populations is needed to confirm the measure's reliability over time.

Why It Matters

By analogy, this study may inform measurement of fatigue severity in ME/CFS, a condition with similar post-exertional worsening patterns. Development of a validated fatigue measure could standardise assessment across research and clinical settings, improving comparability of outcomes in post-infectious illness research. However, the study's specific findings are based on a post-COVID-19 cohort, and direct application to ME/CFS requires further investigation.

Observed Findings

Ten of 17 candidate items fit a unidimensional Rasch model with a theoretical range of 0–21 and were incorporated into the PCS Fatigue Severity Measure V1 (mean 13.8, SD 4.7).
The PCS Fatigue Severity Measure V1 was associated with high correlations (r ≈ |0.8|) with criterion fatigue measures.
The measure was associated with moderate to substantial correlations (r > |0.5|) with pain, physical function, and health rating.
Participants working were observed to have lower fatigue severity scores than those on sick leave (difference: 5.1 points; Cohen's d = 1.08).
Participants meeting criteria for post-traumatic distress or reporting irritability were associated with moderate effect sizes (approximately 0.5) in fatigue scores.

Inferred Conclusions

The authors interpret these findings as evidence that the PCS Fatigue Severity Measure V1 is 'fit for purpose' for quantifying fatigue in post-COVID-19 syndrome at a single point in time.
The authors conclude that the measure meaningfully discriminates between clinical groups (working vs. sick leave) and converges adequately with related constructs (pain, function, health).
The authors infer that further validation in independent samples is necessary before the measure can be recommended for longitudinal or comparative research.

Remaining Questions

Does the PCS Fatigue Severity Measure V1 maintain validity and sensitivity to change in longitudinal follow-up within the same cohort?

What This Study Does Not Prove

This study does not establish causation, generalisability beyond the Quebec cohort, or test the measure's validity over time—the authors explicitly call for longitudinal validation in other populations. The cross-sectional design means the measure's sensitivity to change and test–retest reliability remain unknown. Relevance to ME/CFS is inferred by analogy only and is not directly demonstrated.

Topics

Diagnostics Post-Exertional Malaise

Metadata

DOI: 10.3138/ptc-2023-0093
PMID: 42078679
Evidence level: Single-study or moderate support from human research
Last updated: 5 May 2026

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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 →

Cite this study

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Primary citation

Mayo, Nancy, Brouillette, Marie-Josée, Fellows, Lesley K, & Hum, Stanley (2025). Quantifying the Degree of Fatigue in People Reporting Symptoms of Post-COVID-19 Syndrome: Results from a Rasch Analysis.. Physiotherapy Canada. Physiotherapie Canada. https://doi.org/10.3138/ptc-2023-0093

BibTeX

@article{mecfsatlas-mayo-2025-quantifying-degree,
  author  = {Mayo, Nancy and Brouillette, Marie-Josée and Fellows, Lesley K and Hum, Stanley},
  title   = {Quantifying the Degree of Fatigue in People Reporting Symptoms of Post-COVID-19 Syndrome: Results from a Rasch Analysis.},
  journal = {Physiotherapy Canada. Physiotherapie Canada},
  year    = {2025},
  doi     = {10.3138/ptc-2023-0093},
  note    = {PubMed: 42078679},
  url     = {https://www.mecfsatlas.com/evidence/mayo-2025-quantifying-degree},
}

Atlas snapshot reference

ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-05. https://www.mecfsatlas.com/evidence/mayo-2025-quantifying-degree

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