RT Journal Article SR Electronic T1 Prognosis of Seronegative Patients in a Large Prospective Cohort of Patients with Early Inflammatory Arthritis JF The Journal of Rheumatology JO J Rheumatol FD The Journal of Rheumatology SP 2361 OP 2369 DO 10.3899/jrheum.140082 VO 41 IS 12 A1 Lillian Barra A1 Janet E. Pope A1 John E. Orav A1 Gilles Boire A1 Boulos Haraoui A1 Carol Hitchon A1 Edward C. Keystone A1 J. Carter Thorne A1 Diane Tin A1 Vivian P. Bykerk A1 and the CATCH Investigators YR 2014 UL http://www.jrheum.org/content/41/12/2361.abstract AB Objective. Rheumatoid factor (RF) and anticitrullinated protein antibodies (ACPA) are believed to be associated with more severe rheumatoid arthritis; however, studies in early inflammatory arthritis (EIA) have yielded conflicting results. Our study determined the prognosis of baseline ACPA-negative and RF-negative patients. Methods. Patients enrolled in the Canadian Early Arthritis Cohort had IgM RF and IgG anticyclic citrullinated peptide antibodies 2 (anti-CCP2) measured at baseline. Remission was defined as a Disease Activity Score of 28 joints (DAS28) < 2.6 using logistic regression accounting for confounders at 12-month and 24-month followup. Results. Of the 841 patients, 216 (26%) were negative for both RF and anti-CCP2. Compared to seropositive subjects, seronegative subjects were older (57 ± 15 vs 51 ± 14 yrs), more males proportionately (31% vs 23%), and had shorter length of symptoms (166 ± 87 vs 192 ± 98 days), and at baseline had higher mean swollen joint count (SJC; 8.8 ± 6.8 vs 6.5 ± 5.6), DAS28 (5.0 ± 1.6 vs 4.8 ± 1.5), and erosive disease (32% vs 24%, p < 0.05). Treatment was similar between the 2 groups. At 24-month followup, seronegative compared to seropositive subjects had greater mean change (Δ ± SD) in disease activity measures: ΔSJC counts (−6.9 ± 7.0 vs −5.1 ± 5.9), ΔDAS28 (−2.4 ± 2.0 vs −1.8 ± 1.8), and ΔC-reactive protein (−11.0 ± 17.9 vs −6.4 ± 17.5, p < 0.05). Accounting for confounders, antibody status was not significantly associated with remission. However, at 12-month followup, ACPA-positive subjects were independently more likely to have new erosive disease (OR 2.94, 95% CI 1.45–5.94). Conclusion. Although seronegative subjects with EIA have higher baseline DAS28 compared to seropositive subjects, they have a good response to treatment and are less likely to develop erosive disease during followup.