Background The development of the 2010 classification criteria for rheumatoid arthritis (RA) has led to a redefinition of the patient population, including classification of seropositive vs. seronegative patients. Studies have yielded conflicting results on whether seropositive and seronegative RA are different disease entities.
Objectives Our aim was to compare the disease characteristics of seropositive and seronegative DMARD-naïve early RA patients classified according to the 2010 ACR/EULAR criteria.
Methods RA patients who fulfilled the 2010 ACR/EULAR classification criteria were recruited at 11 rheumatology centers between 2010 and 2013. All patients had symptom duration (from first swollen joint) <2 years, and were DMARD naïve with indication for DMARD treatment. Patients were stratified as seropositive (rheumatoid factor (RF)+, anti-citrullinated peptide antibody (ACPA)+, or both) or seronegative (both RF- and ACPA-) and disease characteristics were compared across the groups using t-test or Wilcoxon rank sum test as appropriate.
Results A total of 237 patients were included with mean (SD) age 51.5 (13.7) years, mean (SD) disease duration 7.1 (5.4) months, and 61.6% female gender. 35 patients (14.8%) were seronegative.
The seronegative patients were older (mean age 56.9 yrs) than seropositive patients (50.5 yrs, p=0.01), while gender distribution was similar; 43% of the seronegative patients and 69% of the seropositive patients did not fulfill the 1987 ACR criteria for RA. Ultrasonography (US) scores, number of swollen joints, DAS44 and Physician Global were significantly higher in seronegative subjects compared to seropositive. However, Richie articular index and patient reported outcome measures were similar between groups.
Conclusions In this cohort of DMARD naïve early RA patients classified according to the 2010 ACR/EULAR criteria, we found that the seronegative patients had higher disease activity, assessed both clinically and by US, than seropositive patients. This may in part be due to the strong weighting of RF and ACPA status in the 2010 criteria, requiring seronegative patients to have involvement of many joints, and thus high disease activity, to fulfill the criteria.
Disclosure of Interest L. Nordberg: None declared, S. Lillegraven: None declared, E. Lie: None declared, A.-B. Aga: None declared, I. Olsen: None declared, T. Uhlig: None declared, D. van der Heijde: None declared, T. Kvien: None declared, E. Haavardsholm Grant/research support from: Abbvie, Pfizer, MSD, Roche, UCB.