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The relationship between polymyalgia rheumatica (PMR) and inflammatory polyarthritis (IP) remains a source of debate in rheumatology: although both conditions have been classified separately as distinct entities, they share many clinical features.1–4 It remains unclear whether synovitis in IP is part of a spectrum of PMR, or if the symptoms of PMR are early manifestations of a distinct diagnosis of IP. Alternatively, the arthritis that develops in PMR might represent a phenotypic transformation in susceptible individuals.
We examined the risk of IP following the diagnosis of PMR in the data from the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk study, a prospective population-based cohort.5 Incident cases of PMR were identified retrospectively among 24 068 volunteers enrolled after 2002 by (1) free-text questionnaire responses at baseline, 18 months, and at 3, 10 and 13 years; (2) linkage to hospital electronic discharge summaries containing International Classification of Diseases codes; and (3) linkage to keyword searches (polymyalgia or rheumatica) of outpatient clinic letters. To be identified as PMR, participants were required to …
Footnotes
Handling editor Josef S Smolen
Contributors MY drafted the manuscript for publication. All authors contributed to the review of drafts of the manuscript. MY, RAW and AJM devised the methodological design for this study. MY carried out all statistical analyses. RL acts as the data guardian and K-TK as the guarantor for the data from EPIC-Norfolk.
Funding EPIC-Norfolk is supported by the Medical Research Council UK (G1000143) and Cancer Research UK (C864/A14136). MY was funded on a Clinical Fellowship by Arthritis Research UK (now known as Versus Arthritis) in order to carry out a PhD and is currently funded by the National Institute for Health Research as a clinical lecturer. The views expressed in this publication are those of the authors and not necessarily those of the NHS, the NIHR, Arthritis Research UK or the Department of Health.
Competing interests None declared.
Patient consent Not required.
Ethics approval The study complies with the Declaration of Helsinki. The Norwich District Health Authority Ethics Committee approved the study and all participants gave written informed consent.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement EPIC-Norfolk custodians and collaborators are committed to open and collaborative analysis. Requests for data sharing are reviewed by the committee and forms can be found at http://www.srl.cam.ac.uk/epic/contact/index.shtml.