Twohig, H, Mitchell, C, Mallen, CD and Muller, SN (2022) Development and psychometric evaluation of the PMR-Impact Scale: a new patient reported outcome measure for polymyalgia rheumatica. Rheumatology. ISSN 1462-0332

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OBJECTIVES: Polymyalgia rheumatica (PMR) causes pain, stiffness and disability in older adults. Measuring the impact of the condition from the patient's perspective is vital to high-quality research and patient-centred care, yet there are no validated patient-reported outcome measures (PROMs) for PMR. We set out to develop and psychometrically evaluate a PMR-specific PROM.

METHODS: Two cross-sectional postal surveys of people with a confirmed diagnosis of PMR were used to provide data for field testing and psychometric evaluation. 256 participants completed the draft PROM. Distribution of item responses was examined and exploratory factor analysis and Rasch analysis were used to inform item reduction, formation of dimension structure and scoring system development. 179 participants completed the PROM at two-time points, along with comparator questionnaires and anchor questions. Test-retest reliability, construct validity and responsiveness were evaluated.

RESULTS: Results from the field-testing study led to the formation of the PMR-Impact Scale (PMR-IS), comprising four domains (symptoms, function, psychological and emotional well-being, and steroid side effects). Construct validity and test-retest reliability met accepted quality-criteria for each domain. There was insufficient evidence from this study to determine its ability to detect flares/deterioration, but the PMR-IS was responsive to improvements in the condition.

CONCLUSION: The PMR-IS offers researchers a new way to assess patient-reported outcomes in clinical studies of PMR. It has been developed robustly, with patient input at every stage. It has good construct validity and test re-test reliability. Further work is needed to fully establish its responsiveness and interpretability parameters and assess its real-world clinical utility.

Item Type: Article
Additional Information: Accepted manuscripts are PDF versions of the author’s final manuscript, as accepted for publication by the journal but prior to copyediting or typesetting. They can be cited using the author(s), article title, journal title, year of online publication, and DOI. They will be replaced by the final typeset articles, which may therefore contain changes. The DOI will remain the same throughout. © The Author(s) 2022. Published by Oxford University Press on behalf of the British Society for Rheumatology. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Uncontrolled Keywords: polymyalgia rheumatica; patient-reported outcomes; psychometrics
Subjects: R Medicine > R Medicine (General)
Divisions: Faculty of Medicine and Health Sciences > School of Medicine
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Depositing User: Symplectic
Date Deposited: 06 Jun 2022 15:21
Last Modified: 21 Jul 2022 12:25

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