ASSOCIATION OF ANTI-CarP LEVELS WITH THE SEROLOGICAL PROFILE IN PATIENTS WITH RHEUMATOID ARTHRITIS

Background: Rheumatoid arthritis (RA) is a systemic autoimmune disease, chronic and inflammatory in nature, which primarily affects the joints and can lead to multisystem involvement. Serologically, a correlation has been observed between the severity of the disease and the presence of certain autoantibodies, such as rheumatoid factor (RF) and anti-citrullinated peptide antibodies (anti-CCP). Recently, anti-carbamylated protein antibodies (anti-CarP) have been described as potential biomarkers for RA, especially in patients who are seronegative for traditionally evaluated antibodies. Objectives: To analyze the relationship between serum levels of anti-CarP antibodies and the serological profile of rheumatoid factor (RF) and anti-CCP in patients with rheumatoid arthritis (RA). Methods: Materials and Methods: A cross-sectional observational study of patients diagnosed with RA and healthy controls (HC). A complete clinical and analytical evaluation was performed, obtaining demographic, clinical, and analytical data. The serological profile of each individual was determined, as well as the levels of anti-CarP antibodies using ELISA. Table 1. FR/anti-CCP (-/ -) n=23 FR/anti-CCP (-/+ ) n=10 FR/anti-CCP (± ) n=7 FR/anti-CCP (+/+ ) n=61 Anti-carP, average (Standard Deviation) 10.61 (8.33) 8.69 (3.99) 10.85 (2.45) 23.78 (21.06) CRP, average (SD) 9.63 (12.49) 9.5 (8.27) 15.24 (19.34) 13.84 (23.25) ESR, average (SD) 19.74 (17.66) 24.9 (13.28) 42.57 (27.09) 34.79 (21.65) RF, average (SD) 11.26 (4.18) 16.2 (7.16) 77.29 (56.3) 213.38 (339.87) Anti-CCP, average (SD) 1.76 (3.37) 197.9 (128.25) 2.51 (2.69) 284.72 (112.34) Results: A total of 101 patients (79% female) with an average age of 45 (±13) years, and 98 healthy controls (67% female) with an average age of 55 (±11) years were included. The patients had significantly higher levels of anti-CarP than the healthy controls (P<0.001), as well as older individuals in general (P=0.004). Upon analyzing the antibody levels, a significant association was observed between elevated levels of anti-CarP and elevated levels of RF (P<0.001). Patients were divided into serological profiles based on the positivity of RF and anti-CCP (see Table 1). Based on the serological profile, patients with double positivity for RF/anti-CCP showed a significantly higher elevation of anti-CarP compared to the rest of the groups (P<0.001). The cutoff value for high levels of anti-CarP was established at twice the standard deviation from the average value of the control population (17.23ng/mL). Thirty-five patients were classified as having elevated anti-CarP, 32 of whom were included in the group with double positivity for RF and anti-CCP (P=0.006), and 3 of them in the group negative for both RF and anti-CCP. No cases of elevated anti-CarP were found in those patients with positive RF or anti-CCP only. Three cases of elevated anti-CarP were also classified among the 98 HCs, without elevation of RF or anti-CCP. Conclusion: Patients with RA have significantly higher serological levels of anti-CarP compared to HCs, and 34.6% of the patients have an elevated anti-CarP profile. High levels of anti-CarP are associated with the combined elevation of RF/anti-CCP. 3% of seronegative RA patients are anti-CarP positive, thereby increasing the seropositive rate from 77% to 80%. REFERENCES: [1] Smolen JS, Aletaha D, Barton A, Burmester GR, Emery P, Firestein GS, et al. Rheumatoid arthritis. Nat Rev Dis Primers. 2018 Feb 8;4:18001. [2] Holers VM. Autoimmunity to citrullinated proteins and the initiation of rheumatoid arthritis. Curr Opin Immunol. 2013;25(6):728-35. Acknowledgements: NIL. Disclosure of Interests: None declared. DOI: 10.1136/annrheumdis-2024-eular.4332 Keywords: Autoantibodies, Diagnostic test, Prognostic factors, Biomarkers Citation: , volume 83, supplement 1, year 2024, page 1666Session: Rheumatoid arthritis (Publication Only)

Autoantibodies, Diagnostic test, Prognostic factors, Biomarkers