SAT0011 What is Undifferentiated Arthritis (UA) in 2013, and can Progression to Rheumatoid Arthritis (RA) be Predicted?
Authors: S. C. Horton, R. J. Wakefield, A. L. Tan, J. E. Freeston, M. H. Buch, P. Emery
Journal: Annals of the Rheumatic Diseases (2013)

<h3>Background</h3> In applying 2010 criteria to patients with early inflammatory arthritis, the weighting of serology in the criteria is such that the majority of ACPA positive arthritis patients are classified as RA. A significant proportion of patients with UA have persistent disease<sup>1,2</sup>. Differences between ACPA negative(-) and ACPA positive(+) patients suggest their disease pathogenesis is divergent. <h3>Objectives</h3> Compare UA and ACPA- RA, and determine clinical and/or ultrasound (US) features predictive of progression to RA. <h3>Methods</h3> DMARD-naïve patients with UA or RA (2010 criteria) with outcomes available at 6 months were selected from the Leeds Early inflammatory arthritis cohort (recruitment since 2010). Steroid within the preceding 4 weeks was an exclusion. Patients with UA were categorised as palindromic, oligo- or polyarthritis according to intermittent or persistent joint tenderness and/or swelling and involvement of &lt;4 or ≥4 joints respectively. <h3>Results</h3> ACPA negativity was observed in 33/37 UA patients and 35/108 RA patients. Baseline characteristics are shown in the table: n(%) or median(IQR), unless otherwise stated. Symptom duration was longer in UA patients, potentially due to a trend towards lower disease activity and lower HAQ in this group. At 6 months, 70% and 89% of patients with UA and ACPA- RA respectively were receiving any DMARD (p=0.08). There were no statistically significant differences (UA vs ACPA- RA) in; median(IQR) DAS44 1.7(1.3-2.4) vs 2.2(1.7-2.7), improvement in DAS44 from baseline 0.7(-0.1-1.3) vs 0.8(0.1-1.7) or HAQ 0.4(0.1-0.8) vs 0.8(0.3-1.0). In patients with UA, 7(19%), 19(51%) and 11(30%) were categorised as palindromic, oligo- and polyarthritis respectively at baseline. Over 6 months, 5/19(26%) of patients with oligoarthritis progressed to polyarthritis, only 1 of these patients(5%) fulfilled 2010 criteria when applied cumulatively. Whereas 3/7(43%) palindromic and 4/11(36%) polyarthritis patients progressed to RA (p=0.02 for comparison between oligoarthritis and palindromic/polyarthritis combined). Of palindromic UA 2 patients had subclinical synovitis on US, both of whom progressed to RA (1 patient was ACPA+). Baseline US findings were not significantly associated with progression to RA or need for DMARD over 6 months amongst oligoarthritis or UA patients overall. <h3>Conclusions</h3> Clinically important levels of disease activity and disability exist in patients with UA. Differences in clinical phenotype of patients with UA may be predictive of disease progression. <h3>References</h3> Krabben A, et al. <i>ARD</i> 2012;71(2):238-41. van der Helm-van Mil A, Huizinga TW. <i>ARD</i> 2012;71:1596-8. <h3>Disclosure of Interest</h3> S. Horton: None Declared, R. Wakefield: None Declared, A. L. Tan: None Declared, J. Freeston: None Declared, M. Buch Consultant for: Abbot, Pfizer, Roche, Chugai, BMS, UCB, P. Emery Consultant for: Abbot, Pfizer, Roche, Chugai, BMS, UCB, MSD