{
  "abstract": "Purpose: To develop and psychometrically evaluate a new scale measuring post-exertional malaise in people with myalgic encephalomyelitis (ME)/ chronic fatigue syndrome (CFS). Methods: A draft scale was co-produced with patient and clinician advisory groups. After extensive pilot testing, adults with ME/CFS completed the Post Activity Symptom Scale online and repeated it two weeks later to assess test-retest reliability and sensitivity to change. Rasch analysis assessed each domain for unidimensionality, targeting, internal reliability, item fit and local dependency. Then Rasch-transformed interval data and parametric statistics were used to assess criterion-related and discriminant validity (by comparison with measures of physical health and ME/CFS severity), test-retest reliability and minimal detectable difference. Results: The item regarding delay in PEM onset was an under-discriminating misfit anomaly which was inconsistent with the remaining PASS items. When this was removed, the PASS was a unidimensional, psychometrically robust scale. Criterion-related validity (r=0.58, p<0.001) was moderate and highly significant, discriminant validity (p<0.001) and test-retest reliability (ICC = 0.81) were excellent. The minimal detectable difference was 1.93/100. Participants found the PASS easy to complete, comprehensive and relevant. Conclusion: The Post Activity Symptom Scale is a valid, reliable, sensitive measure of people of PEM in ME/CFS",
  "abstract_shown": true,
  "affiliations": [
    "University of Manchester.ac.uk"
  ],
  "article_type": "PUBLISHAHEADOFPRINT",
  "arxiv": null,
  "author_total": 3,
  "authors": [
    {
      "name": "M. Horton"
    },
    {
      "affs": [
        0
      ],
      "name": "S. F. Tyson"
    },
    {
      "name": "R. Fleming"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/cas5rmxyknzv4.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.11.06.26367424",
  "fulltext_url": "https://www.medrxiv.org/content/10.64898/2026.11.06.26367424v1.full",
  "id": "cas5rmxyknzv4",
  "issns": [],
  "landing_url": "https://www.medrxiv.org/content/10.64898/2026.11.06.26367424v1",
  "language": null,
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "medrxiv",
      "rehabilitation medicine and physical therapy"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://www.medrxiv.org/content/10.64898/2026.11.06.26367424v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-06",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/cas5rmxyknzv4.ris",
  "sources": [
    {
      "first_seen": "2026-11-09T00:20:54Z",
      "native_id": "10.64898/2026.11.06.26367424",
      "source": "medrxiv",
      "url": "https://www.medrxiv.org/content/10.64898/2026.11.06.26367424v1"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "medrxiv:rehabilitation medicine and physical therapy",
      "subfield": "general"
    }
  ],
  "title": "The development and psychometric evaluation of the Post Activity Symptom Scale (PASS) for Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome.",
  "title_text": "The development and psychometric evaluation of the Post Activity Symptom Scale (PASS) for Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome.",
  "type": "preprint",
  "updated_at": "2026-11-09T12:20:30Z",
  "url": "https://research.draconitic.com/paper/cas5rmxyknzv4",
  "venue": "medRxiv",
  "versions": []
}