Pos0396 disease severity is associated with low bone mineral density and osteoporosis in patients with systemic lupus erythematosus

Background Patients with systemic lupus erythematosus (SLE) are at an increased risk for osteoporosis and fragility fractures.[1] This risk is mediated by a variety of factors such as chronic inflammation, treatment with glucocorticoids (GC), vitamin D deficiency, and others.[2] The role of disease-specific factors of SLE has not been fully elucidated. Objectives We aimed to identify factors associated with bone mineral density and osteoporosis including fragility fractures to better understand the interplay between disease-specific factors and general risk factors that drive bone loss in this patient population. Methods Rh-GIOP is a prospective observational cohort study investigating bone health in consecutive patients ≥18 years with inflammatory rheumatic diseases and current or prior GC treatment. This cross-sectional analysis assessed the baseline visits of all patients with SLE fulfilling the EULAR/ACR 2019 SLE classification criteria. Multivariable linear regressions models were fitted to identify factors associated with bone mineral density (BMD). As a second outcome, we investigated factors associated with clinical osteoporosis (defined by either a T-Score of ≤ -2,5, anti-osteoporotic treatment and/or fragility fractures) by multivariable logistic regression analysis. Results Baseline data from 110 patients with SLE were analyzed. The mean age was 48.1±14.5 years, mean disease duration 16.3±9.9 years, and 41% of the cohort was identified as having osteoporosis (OP). Lupus nephritis was present in 35% of the SLE patients, of whom 55% had active nephritic disease at baseline osteoporosis screening visit. Class IV and V accounted for most nephritis cases (61%). In multivariable linear regression analysis, lupus nephritis class IV and V (reg. coefficient (95%CI): -0.745 (-1.395;-0.095)), the presence of U1-RNP antibodies (-0.750 (-1.314;-0,187)) as well as C-reactive protein (CRP, -0.015 (-0.026;-0.003)) and longer disease duration (-0.037 (-0.056;-0.018)) were significantly associated with low BMD. Conversely, clinical remission (defined as SLEDAI-2K=0 and GC dosage ≤5 mg prednisone equivalent per day) was positively associated with BMD (0.447 (0.037;0.857)), as were Siglec-1 levels on monocytes as surrogate for Type-I interferon activity (0.558 (0.150;0.967)), BMI (0.045 (0.014;0.076)), and health assessment questionnaire (HAQ, 0.307 (0.078;0.536)). In multivariable logistic regression analysis, active lupus nephritis (OR (95%CI): 7.42 (1.256;43.868)) was strongly associated with OP in patients with SLE. Additionally, age (1.06 (1.020;1.100)), HAQ (0.29 (0.120;0.682)) and complement factor 3 (1.27 (1.002;1.601)) were found to be significantly related to the presence of OP. Neither current GC use, cumulative GC dose nor GC duration were significantly associated with BMD or clinical OP. Conclusion In patients with SLE, indicators of disease severity, expressed by (active) lupus nephritis, high CRP, U1-RNP antibodies, and long disease duration, are related to poor bone health in addition to commonly known risk factors such as low BMI and higher age. The knowledge of these disease-specific factors helps to identify patients with SLE at particular high risk for OP and fragility fractures. References [1]Wang X, Yan S, Liu C, Xu Y, Wan L, Wang Y, et al. Fracture risk and bone mineral density levels in patients with systemic lupus erythematosus: a systematic review and meta-analysis. Osteoporos Int. 2016;27(4):1413-23. [2]Bultink IE, Lems WF. Systemic lupus erythematosus and fractures. RMD Open. 2015;1(Suppl 1):e000069. Acknowledgements: NIL. Disclosure of Interests Edgar Wiebe Speakers bureau: Medac and Novartis, Consultant of: Medac and Novartis, Elisa Celine Schilling: None declared, Dörte Huscher: None declared, Andriko Palmowski: None declared, Zhivana Boyadzhieva: None declared, Sandra Hermann: None declared, Burkhard Muche Speakers bureau: Amgen, UCB, Galapagos Biopharma, Consultant of: Amgen, UCB, Galapagos Biopharma., Tobias Alexander Speakers bureau: Abbvie, Amgen, AstraZeneca, Bayer, Janssen, GSK, Lilly, Medac, Pfizer, Consultant of: Abbvie, Amgen, AstraZeneca, Bayer, Janssen, GSK, Lilly, Medac, Pfizer, Falk Hiepe: None declared, Frank Buttgereit Speakers bureau: Abbvie, Horizon Therapeutics, Pfizer, and Roche, Consultant of: Abbvie, Horizon Therapeutics, Pfizer, and Roche, Grant/research support from: Horizon Therapeutics, Roche and Abbvie.