SAT0515 Seropositive Rheumatoid Arthritis has a Distinctive Bone Phenotype at the Ultra-Distal Radius Compared to Seronegative Rheumatoid Arthritis and Psoriatic Arthritis
Authors: R. Kocijan, S. Finzel, M. Englbrecht, A. Kleyer, J. Rech, G. Schett
Journal: Annals of the Rheumatic Diseases (2013)

<h3>Background</h3> Psoriatic arthritis (PsA) and rheumatoid arthritis (RA) are chronic inflammatory joint diseases characterized by periarticular and systemic bone loss. As a consequence, fracture risk is increased in both disorders. However, pathogenesis and radiological characteristics are different and areal bone mineral density, measured by dual-energy x-ray absorptiometry (DXA) does not reflect bone status adequately in PsA and RA. <h3>Objectives</h3> The aim of this study was to compare bone quality, including volumetric bone density (vBMD) and microstructure of trabecular and cortical bone, assessed by high-resolution peripheral quantitative computed tomography (Xtreme-CT) in patients with PsA and RA at the distal radius. <h3>Methods</h3> We investigated 50 patients with PsA (24 female, 26 male, mean age 50.5 ± 13.1 years, PsA) and 60 patients with RA (33 female, 27 male, mean age 53.7 ± 12.3 years, RA). RA was divided into seropositive RA (Anti-cyclic citrullinated peptide antibody (anti-CCP) and/or rheumatoid factor (RF) positive, RA+, n=38) and seronegative RA (RA-, n=22). HR-pQCT measurements (Xtreme-CT, Scanco Medical AG, Brüttisellen, Switzerland) were carried out at the ultra-distal radius using the manufacturer's standard protocol. Scanning was performed within a region of 110 slices proximal to the reference line. Data were compared between RA+, RA- and PsA. In addition, correlations between demographic data, vBMD and microstructure were carried out in all subgroups. <h3>Results</h3> Patients with RA did not differ from patients with PsA regarding age, BMI, duration of disease, DAS28, CRP or HAQ. Erosions were detected in 72% (RA) and 70% (PsA) of patients, respectively. No significant differences were found for vBMD or structure parameters between RA and PsA and RA- and PsA. However, RA+ showed significantly decreased values for total trabecular bone density (Dtrab, p=0.007), the peripheral trabecular density adjacent to the cortex (Dmeta, p=0.002) and the central medullary trabecular density (Dinn, p=0.021) compared to PsA. Moreover, trabecular bone volume fraction (BV/TV, p=0.007) and trabecular number (Tb.N, p=0.044) were significantly lower in RA+. In addition, trabecular separation (Tb.Sp, p=0.046) was significantly increased in RA+ compared to PsA. Significantly lower trabecular density parameters (Dtrab, p=0.007; Dmeta, p=0.007; Dinn, p=0.014) and microstructure including BV/TV (p=0.007) and Tb.N (p=0.08) as well as increased Tb.Sp (p=0.016) were also found for RA+ in comparison to RA-. <h3>Conclusions</h3> Our data strongly suggest a distinct bone phenotype in RA+ compared to RA- and PsA. RA+ shows significantly lower trabecular vBMD and low quality microstructure of the bone, independently from age. Autoantibody status thus seems to play a dominant role, not only in local, but also in systemic bone loss. <h3>Disclosure of Interest</h3> R. Kocijan Grant/research support from: Bayerische Forschungsstiftung, S. Finzel: None Declared, M. Englbrecht: None Declared, A. Kleyer: None Declared, J. Rech: None Declared, G. Schett: None Declared