Pos0628 Erosive Progression Assessed by High-Resolution Peripheral Quantitative Computed Tomography Compared to Conventional Radiography: A One-Year Cohort Study in 310 Patients With Established Rheumatoid Arthritis

Background: The gold standard to monitor bone erosions in patients with rheumatoid arthritis (RA) is conventional radiography (CR). However, CR has a low sensitivity for detecting bone erosions (1). High-resolution peripheral quantitative computed tomography (HR-pQCT) is a sensitive imaging modality that is well suited for detecting bone erosions, as it provides high-resolution, three-dimensional images of the distal joints with low radiation exposure (2,3). A recent cross-sectional study has documented that HR-pQCT of two joints and CR of 44 joints have comparable diagnostic accuracies to classify patients as having erosive disease (4). Whether HR-pQCT adds information to that of CR for detecting erosive progression needs to be investigated. Objectives: To investigate the diagnostic accuracy of HR-pQCT to detect erosive progression during one year compared to CR in RA. Methods: This prospective study included 359 patients with established RA (disease duration ≥ 5 years) between March 2018 and October 2020 (Figure 1). HR-pQCT and CR were obtained at inclusion and after one year. Erosive assessment was performed at two metacarpophalangeal joints of the dominant hand using HR-pQCT and progression was defined as an increase in erosion number ≥ 1 or an increase in erosive volume > least significant change. CR of hands, wrists, and feet were evaluated using Sharp/van der Heijde scores and erosive progression was defined as a 1.1-point increase in erosion score according to the smallest detectable change. Results: In paired analyses (n=310), erosive progression was identified in 30 patients using CR and in 40 patients using HR-pQCT (Table 1). In the 40 patients with erosive progression on HR-pQCT, progression was not identified by CR in 33 patients. Adding HR-pQCT doubled the proportion of patients identified with progression from 30 (10%) to 63 (20%) patients. Using CR as reference, the sensitivity (% (95% CI)) of HR-pQCT for identifying erosive progression was 23.3 (9.9–42.3) and the specificity was 88.2 (83.8–91.7). Conclusion: A substantial proportion of patients with erosive progression are overlooked using only CR to monitor erosive progression. Adding high-resolution peripheral CT doubles the proportion of patients, who may benefit from individualized therapy targeting erosive progression in established RA. REFERENCES: [1] Dohn UM, Ejbjerg BJ, Hasselquist M, et al. Detection of bone erosions in rheumatoid arthritis wrist joints with magnetic resonance imaging, computed tomography and radiography. Arthritis Res Ther. 2008;10:R25. [2] Gruneboom A, Kling L, Christiansen S, et al. Next-generation imaging of the skeletal system and its blood supply [review]. Nat Rev Rheumatol. 2019;15:533-549. [3] Klose-Jensen R, Tse JJ, Keller KK, et al. High-resolution peripheral quantitative computed tomography for bone evaluation in inflammatory rheumatic disease [review]. Front Med. 2020;7:337. [4] Klose-Jensen R, Therkildsen J, Blavnsfeldt AG, et al. Diagnostic accuracy of high-resolution peripheral quantitative computed tomography and X-ray for classifying erosive rheumatoid arthritis. Rheumatology (Oxford). 2022;61:963-973. Acknowledgements: The authors are very grateful for the contribution from the listed foundations and study participants. The project would not have been possible without all the work performed by the clinical staff involved in the study. In particular, Jette Barlach, Mia Marie Remmer, Lone Thomasen, Marie Bækmark Kjær, Else Sloth Rousing, and Birgit Winther Friis are gratefully acknowledged for their excellent assistance. Likewise, we want to express our sincere gratitude to the staff at the Osteoporosis Clinic and Ditte Kofoed for technical support and assistance with the HR-pQCT equipment. Furthermore, we are truly grateful for the collaboration with the staff at ManskeLab, Calgary, Canada and their extensive expertise in erosion segmentation and 3D slicer. We acknowledge the assistance and recent update of the BAM-Erosion module provided by Yousif Al-Khoury in collaboration with ManskeLab. Disclosure of Interests: Josephine Therkildsen: None declared, Rasmus Klose-Jensen: None declared, Mathias Hänel: None declared, Bente Langdahl I have received honorariums from Amgen, UCB, Eli Lilly, Gedeon-Richter and Astellas., I have worked as a consultant for Amgen, UCB, Gedeon-Richter, Eli Lilly and Gedeon., I have received research grants from Amgen and the Novo Nordic Foundation., Jesper Thygesen: None declared, Jesper S. Thomsen I have received a research grant from Keros Therapeutics for an unrelated study., Sarah L. Manske: None declared, Kresten Keller: None declared, Ellen-Margrethe Hauge I have received fees for speaking and/or consulting from Novo, Novartis, AbbVie, Sanofi, Sobi., I have been principal investigator in trials by SynACT Pharma and involved as site principal investigator in trials by AbbVie, Novartis, Novo Nordisk and Sanofi., I have received fees for speaking and/or consulting from Novo, Novartis, AbbVie, Sanofi and Sobi., I have received research funding to Aarhus University Hospital from: Novo Nordic Foundation, Danish Regions Medicine Grants, Galapagos, and AbbVie and I have received funding to cover travel expenses from Pfizer, Sobi, and AbbVie.