POS0444 DIAGNOSTIC VALUE OF HIGH-RESOLUTION PERIPHERAL QUANTITATIVE COMPUTED TOMOGRAPHY COMPARED TO CONVENTIONAL RADIOGRAPHY FOR DETECTING EROSIVE DISEASE IN RHEUMATOID ARTHRITIS
Authors: R. Klose-Jensen, J. Therkildsen, A. B. Blavnsfeldt, B. Langdahl, K. K. Keller, E. M. Hauge
Journal: Annals of the Rheumatic Diseases (2021)

Background: Conventional radiography (CR) of the hands, wrists and feet is currently the gold standard for assessing erosive damage in patients with rheumatoid arthritis (RA). However, CR is prone to relatively low resolution and projection superimposition due to 2-dimensional imaging. Therefore, CR might not detect erosive disease in RA patients. High-resolution peripheral quantitative computed tomography (HR-pQCT) is an imaging modality with superior resolution (82µm 3 ) to all other imaging modalities in vivo. However, HR-pQCT imaging is limited by a smaller field of view. Therefore, it needs to be illuminated, whether the higher resolution of HR-pQCT imaging is sufficient for diagnosing erosive disease in patients with RA despite the limited field of view. Objectives: The objective was to investigate whether High-Resolution peripheral Quantitative Computed Tomography (HR-pQCT) of just two metacarpophalangeal (MCP) joints can diagnose more patients having erosive RA than conventional radiography (CR) of 44 joints in the hands, wrist and feet. Methods: In this single-centre cross-sectional study. Patients with established RA (disease duration ≥ 5 years) were investigated by HR-pQCT and CR. The second and third MCP joints of the dominant hand were assessed for erosions by HR-pQCT. CR in the hands, wrist and feet were scored according to the Sharp/van der Heijde (SHS) method. Results: Three hundred fifty-four patients were included. By CR, 67 (18.9%) patients were classified with non-erosive RA, and 287 (81.1%) with erosive RA. In the 67 patients with non-erosive RA, 47 patients (70.1%) had erosions in the second and third MCP joints by HR-pQCT (Figure 1). We found an agreement between CR and HR-pQCT for 274 (77.4%) of the patients. The sensitivity and specificity (95%CI) of HR-pQCT for diagnosing erosive RA when CR of hands, wrist and feet were used as the reference was 89% (84 – 92) % and 30% (19 – 42) %, respectively. Using HR-pQCT for two MCP joints as the reference, the sensitivity and specificity of CR of hands, wrist and feet for diagnosing erosive RA were 84% (80 – 88) % and 38% (25 – 52) %, respectively. The McNemar’s χ 2 test for diagnosing patients having erosive RA between the two modalities was 2.45, p = 0.146. Conclusion: HR-pQCT imaging identifies erosions which are not seen by CR. Using HR-pQCT at of the second and third MCP joint reclassified a substantial number of patients as having erosive RA compared to their non-erosive state determined by CR. The sensitivity and specificity of diagnosing patients having erosive RA using HR-pQCT from only two fingers were not statistically different from CR of 44 joints, in the hands, wrist and feet. Acknowledgements: The authors, we want to acknowledge Aarhus University, The Danish Rheumatism Association, Novo Nordic Foundation and A.P. Møller Fonden who have financially supported the study. The funding sources did not have any role in the collection, analysis and interpretation of data. The authors are grateful for the excellent assistance in recruiting and scheduling the patients by Mia Marie Remmer, Lone Thomasen and Else Sloth Rousing. Disclosure of Interests: Rasmus Klose-Jensen: None declared, Josephine Therkildsen: None declared, Anne-Birgitte Blavnsfeldt: None declared, Bente Langdahl Speakers bureau: Eli Lilly, Amgen, UCB, Gilead, and Gideon-Richter, Grant/research support from: Novo Nordisk and Amgen, Kresten Krarup Keller: None declared, Ellen-Margrethe Hauge Speakers bureau: MSD, Pfizer, UCB, and Sobi., Grant/research support from: Roche, Novartis and Novo Nordic Foundation.