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Comparison of long term outcome of patients with rheumatoid arthritis presenting with undifferentiated arthritis or with rheumatoid arthritis: an observational cohort study

J van Aken^1,*, H van Dongen^1,*, S le Cessie², C F Allaart¹, F C Breedveld¹, T W J Huizinga¹

¹ Department of Rheumatology, Leiden University Medical Centre, Leiden, The Netherlands
² Department of Medical Statistics, Leiden University Medical Centre, Leiden, The Netherlands

Correspondence to:
Professor T W J Huizinga
Department of Rheumatology, Leiden University Medical Centre, PO Box 9600, 2300 RC, Leiden, The Netherlands; T.W.J.Huizinga{at}lumc.nl

Background: The outcome of undifferentiated arthritis (UA) ranges from remission to rheumatoid arthritis (RA) fulfilling the American College of Rheumatology (ACR) classification criteria.

Objectives: To report the outcome of UA after 1 year of follow up and compare the disease course of patients who presented with UA, but evolved into RA within 1 year (UA-RA group), with that of patients who presented with RA fulfilling the ACR criteria (RA-RA group).

Methods: The diagnosis of 330 patients who presented with UA was recorded at 1 year. The UA-RA and RA-RA groups were then followed up for 3 more years. Outcome measurements were radiographic progression, disease activity, and functional capacity.

Results: From 330 patients who were diagnosed UA, 91 had evolved into RA at 1 year; 62 patients had presented with RA. No significant differences were detected between the UA-RA and RA-RA groups in median Sharp/van der Heijde score at baseline, radiographic progression rates, disease activity, and functional capacity. However, significantly more disease modifying antirheumatic drugs were prescribed in the RA-RA group.

Conclusion: The disease outcome of patients who present with UA that evolves into RA within 1 year is the same as that of patients who present with RA as measured by radiographic progression, disease activity, and functional capacity.

Abbreviations: ACR, American College of Rheumatology; CCP, cyclic citrullinated peptide; CRP, C reactive protein; DAS, Disease Activity Score; DMARD, disease modifying antirheumatic drug; EAC, Early Arthritis Clinic; ESR, erythrocyte sedimentation rate; HAQ, Health Assessment Questionnaire; RA, rheumatoid arthritis; RF, rheumatoid factor; UA, undifferentiated arthritis

Keywords: undifferentiated arthritis; rheumatoid arthritis; radiographic progression; joint damage; disease outcome

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