THU0089 ASSOCIATION OF ANTI-PAD4 ANTIBODIES WITH EROSION AND BIOLOGICAL TREATMENT USE IN RHEUMATOID ARTHRITIS

Background: Novel biomarkers have been described in rheumatoid arthritis (RA) patients, including antibodies to carbamylated proteins (anti-CarP) and to protein-arginine deiminases (PAD). Anti-PAD4 antibodies are associated with anti-citrullinated protein antibodies (ACPA) and worse baseline radiographic joint damage [1]. A subset of anti-PAD4 antibodies that cross-react with PAD3 and are associated with erosive disease, ACPA and progress despite treatment have also been described [1]. Objectives: To evaluate several novel RA markers in a cohort of RA and controls and their association with erosive disease and biological treatment use in RA. Methods: Sera from 116 RA patients [63 young onset RA (YORA) and 53 elderly onset RA (EORA)] and 155 controls [134 polymyalgia rheumatica (PMR) patients and 21 healthy individuals (HI) older than 60 years old] were included. Information on erosion status and biological treatment was available for 56 of the RA patients. The samples were tested for anti-PAD3 and anti-PAD4 IgG using the novel particle-based multi-analyte technology (PMAT, research use only, RUO), as well as for ACPA [CCP3 IgG ELISA and chemiluminescent immunoassay (CIA)] and anti-CarP IgG (ELISA, RUO). Results: Significantly higher levels of anti-PAD3, anti-PAD4 and ACPA (ELISA and CIA) but not CarP were observed in YORA vs. EORA (p Conclusion: Anti-PAD3, anti-PAD4 and ACPA are associated with disease onset at an early age. Anti-PAD4 are associated with erosive disease and biological treatment use in RA and represent a useful marker for better patient stratification. Reference: [1] Darrah, E., et al., Erosive rheumatoid arthritis is associated with antibodies that activate PAD4 by increasing calcium sensitivity. Sci Transl Med, 2013. 5(186): p. 186ra65. Disclosure of Interests: Laura Martinez-Prat Employee of: Inova Diagnostics (Not pharmaceutical, diagnostics company), Victor Martinez-Taboada: None declared, Marcos Lopez-Hoyos Consultant for: Inova Diagnostics (Not pharmaceutical, diagnostics company), Michael Mahler Employee of: Inova Diagnostics (Not pharmaceutical, diagnostics company)