LAUSR

EULAR recommendations for early arthritis recommend assessing the following risk factors for persistent disease in Undifferentiated Arthritis (UA): polyarthritis, acute phase reactants (i.e. c-reactive protein(CRP), erythrocyte sedimentation rate(ESR)), rheumatoid factor (RF), ACPA and imaging findings/erosions. However, these recommendations are based on an outdated definition of UA: not fulfilling 1987 RA criteria and having no alternative diagnosis (‘conventional UA’). Since the introduction of the 2010 RA criteria the characterization of UA has changed. The contemporary definition of UA is: not fulfilling 1987- nor 2010 criteria, and having no alternative diagnosis. Therefore, predictors for persistent disease in conventional UA may not be applicable in contemporary UA.Our objective was to assess which risk factors for persistent disease, as mentioned in the EULAR recommendations, are applicable in contemporary UA.Patients consecutively included in the Leiden Early Arthritis Clinic cohort with contemporary UA between 2006-2019, when DMARD start in UA was recommended, were studied. The outcome was sustained remission, defined as absence of clinical synovitis without DMARD use (including corticosteroids) for the entire follow-up (at least one year). Cox regression was used to test the association between the risk factors as mentioned in EULAR-guidelines and sustained remission. For comparison, patients with conventional UA (not fulfilling the 1987 criteria and no other diagnosis) were studied using similar analyses.Contemporary UA patients (n=710) were mostly ACPA negative (95%) and had a median of 2 swollen joints. Radiographic erosions were rare (1.8%). 60% of contemporary UA patients achieved sustained remission after median 1.5 years (IQR 1-3). After achieving remission patients were followed for 5.5 years without clinical arthritis, demonstrating sustainability. Univariably, CRP, ESR, ACPA and RF were associated with time to sustained remission, while polyarthritis was not. In multivariable analysis, only ACPA and CRP were independently associated with sustained remission (HR 0.10 (95%CI:0.03-0.32) and HR 0.67(0.50-0.91), respectively). 67% of contemporary UA patients had none of these risk factors. In contrast, only 2% had both CRP and ACPA. For comparison, multivariable analysis in conventional UA patients showed that ACPA, RF, CRP and polyarthritis were all independently associated with sustained remission.The contemporary UA population is different from conventional UA and risk factors for disease persistence are partly dissimilar. ACPA and CRP remain to be predictive in contemporary UA. Other factors included in the current EULAR recommendation were uninformative (RF, ESR, polyarthritis) or rare (erosions). Therefore, risk factors recommended in future EULAR recommendations may require alterations.None declared