SAT0084 Anti-carbamylated protein antibodies as potential biomarkers of disease activity in early arthritis patients
Authors: A. Gonzalez, C. Regueiro, A.M. Ortiz, L. Nuño, D. Peiteado, A. Villalba, D. Pascual-Salcedo, A. Martinez-Feito, A. Balsa, I. Gonzalez-Alvaro
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> It has become increasingly clear that appropriate initial management of rheumatoid arthritis (RA) increases the chances of success and improves long-term prognosis. Therefore, rheumatologists need prognostic biomarkers to select patients requiring aggressive management. It is possible that anti-carbamylated protein antibodies (anti-CarPA) may serve as such biomarkers because they are associated with erosions and their progression, and with mortality in some studies. Recently, the possibility that they are also associated with disease activity in early arthritis (EA) has been examined by several studies with discordant results. <h3>Objectives</h3> We aimed to explore the relationship between variation in disease activity and anti-CarPA in EA patients. <h3>Methods</h3> EA patients from two prospective clinics, Hospital Universitario La Paz (n=492) and Hospital Universitario La Princesa (n=501), were included. DAS28 was available at baseline and at months 6 (M6), 12 (M12) and 24 (M24) of follow-up. Anti-CarPA were determined in baseline serum samples by ELISA using <i>in vitro</i> carbamylated fetal calf serum. Student t test and main effects general linear regression were used for analysis. <h3>Results</h3> The 27.4% of EA patients that were positive for anti-CarPA showed higher DAS28 at baseline than the negative patients (4.93 <i>vs</i> 4.31, p=1.6x10–<sup>8</sup>). The difference persisted at all visits during follow-up (3.60 <i>vs</i> 3.19 at M6; 3.47 <i>vs</i> 3.09 at M12; and 3.31 <i>vs</i> 2.79 at M24; all with p≤0.001). These differences were independent of patient sex and age, smoking, time since symptoms onset, the specific EA clinic and the year of onset. In addition, they persisted after accounting for the presence of RF or ACPA at baseline (p=1.3x10–<sup>5</sup>, and p=5.7x10–<sup>5</sup>, respectively) and at later visits (p&lt;0.05 for all analyses). Analysis of the relation between anti-CarPA and ΔDAS28 showed association only with ΔDAS28 from baseline to M6 (p=0.005). In this period, the positive patients showed less decrease of DAS28 than the negative patients. This was independent of all the variables mentioned above and of the initial DAS28. As a result of this association, 20.5% of the anti-CarPA positive patients reached remission at M6, in comparison with 34.6% of the negative patients. In contrast, ΔDAS28 from M6 to M12 and from M12 to M24 were small and not associated with anti-CarPA. <h3>Conclusions</h3> Anti-CarPA were associated with high disease activity at presentation and with less improvement in the first 6 months of follow-up in EA patients. These results reinforce the possibility that anti-CarPA could be useful in the clinic as prognostic biomarkers. <h3>Acknowledgements</h3> Supported by grants PI14/01651 and RD16/0012/0014,/0011,/0012 of the Instituto de Salud Carlos III (Spain) that are partially financed by the ERDF <h3>Disclosure of Interest</h3> None declared