AUTOANTIBODIES ARE ASSOCIATED WITH EROSIVE DAMAGE IN THE SECOND AND THIRD METACARPOPHALANGEAL JOINTS ASSESSED BY HIGH-RESOLUTION PERIPHERAL QUANTITATIVE COMPUTED TOMOGRAPHY IN PATIENTS WITH RHEUMATOID ARTHRITIS.

Background: The presence of anti-citrullinated protein antibodies (ACPAs) and rheumatoid factor (RF) are prognostic for erosive severity by radiography in patients with rheumatoid arthritis (RA) [1]. However, others have shown that RF mainly acts as an enhancer for ACPAs mediated bone loss [2]. High-resolution peripheral quantitative computed tomography (HR-pQCT) has a very high resolution with a voxel size of 82 µm , and has been proposed to monitor disease activity in patients with RA. In the current study, erosive damage was assessed by HR-pQCT according to the presence of autoantibodies. The hypothesis is that the presence of RF and especially ACPA is associated with erosive damage in two metacarpophalangeal (MCP) joints assessed by HR-pQCT; this has previously been shown using 44 joints assessment of both hands and feet by conventional radiography. Objectives: The objective was to investigate if the presence of the autoantibodies, RF and ACPAs, was associated with a higher erosive burden in two MCP joints assessed by HR-pQCT. Methods: Patients with RA and disease duration ≥ 5 years had their second and third MCP joints imaged by HR-pQCT. Age, sex, disease duration, ACPAs and RF status were acquired. From the Danish Clinical Quality Program – The Danish Rheumatologic Database (DANBIO) [3], the average 28-joint Disease Activity Score (DAS28-CRP) and Health Assessment Questionnaire (HAQ) from five years before inclusion were extracted. Statistical significance was investigated for the following groups, who were ordered according to the expected erosive burden: RF+/ACPA+ patients, RF-/ACPA+ patients, RF+/ACPA- patients, and autoantibodies negative patients. Analysis of variance was used to investigate the difference between the groups for age and sex. Cuzick’s Rank-sum test for trend of ordered groups was used to test for trend for disease duration, 5-year average HAQ, 5-year average DAS28, number of erosions, total erosive volume, and average erosion volume. Results: A total number of 353 patients with RA were included in this study. 203 was RF+/ACPA+ positive, 52 was RF-/ACPA+ positive, 24 were RF+/ACPA- positives, and 74 were autoantibodies negative. The groups were comparable with respect to age, sex distribution, disease duration and mean disease activity during the last five years, according to mean DAS28-CRP and mean HAQ during the previous five years. There was a statistically significant test for trend for total erosive volume ( p = 0.016) and average erosion volume ( p = 0.043), but not for the number of erosions ( p = 0.053) ( Figure 1 ). A significant difference between the groups was only observed between double-positive patients and patients negative for autoantibodies. Figure 1. Scatterplot showing the number of erosions (A), total erosive volume (B) and the average volume of erosions (C) in the second and third MCP joint per patient according to the presence of the autoantibodies, ACPAs, as well as RF. Boxes denote the median and 25 and 75 percentile of the groups. Conclusion: In the current study, HR-pQCT scanning of only two MCP joints supports previous findings by radiography of both hands and feet, showing the accumulated erosive burden is higher in patients double-positive for RF and ACPA. REFERENCES: [1]Syversen SW, Gaarder PI, Goll GL, et al. High anti-cyclic citrullinated peptide levels and an algorithm of four variables predict radiographic progression in patients with rheumatoid arthritis: results from a 10-year longitudinal study. Ann Rheum Dis 2008; 67 :212–7. doi:10.1136/ARD.2006.068247 [2]Hecht C, Englbrecht M, Rech J, et al. Additive effect of anti-citrullinated protein antibodies and rheumatoid factor on bone erosions in patients with RA. Ann Rheum Dis 2015; 74 :2151–6. doi:10.1136/annrheumdis-2014-205428 [3]Ibfelt EH, Jensen DV, Hetland ML. The Danish nationwide clinical register for patients with rheumatoid arthritis: DANBIO. Clin Epidemiol 2016; 8 :737–42. doi:10.2147/CLEP.S99490 Disclosure of Interests: Rasmus Klose-Jensen: None declared, Josephine Therkildsen: None declared, Anne-Birgitte Blavnsfeldt: None declared, Bente Langdahl Speakers bureau: Amgen, UCB, Eli Lilly, Gedeon-Richter, Astellas, Consultant of: Amgen, UCB, Gedeon-Richter, Eli Lilly, Gedeon., Grant/research support from: Amgen, Novo Nordisk, Jesper Thygesen: None declared, Kresten Keller: None declared, Ellen-Margrethe Hauge Speakers bureau: AbbVie, Sanofi, Sobi, MSD, UCB, Consultant of: AbbVie, Sanofi, Sobi, MSD, UCB, Grant/research support from: Research funding to Aarhus University Hospital from Novo Nordic Foundation, Danish Rheumatism Association, Danish Regions Medicine Grants, Roche, Novartis. Travel expenses from Celgene, MSD, Pfizer, Roche, Sobi. Citation: , volume 81, supplement 1, year 2022, page 1030Session: Diagnostics and imaging procedures (POSTERS only)