Ab0890 Prominent Osteoproliferative Changes of the Axial Spine in the Presence of Chronic Kidney Disease Accompanying Spondyloarthritis Patients

Background: Axial spondyloarthritis (axSpA) is an immune-mediated inflammatory disease characterised by new bone formation on the axial joint, reflecting enthesitis [1]. In the presence of comorbidities affecting bone metabolism, such as chronic kidney disease (CKD) accompanying axSpA, radiographic interpretation of axial spinal lesions is challenging. Objectives: The aim of this study was to compare spinal radiographic changes in axSpA-CKD patients on bDMARD therapy with axSpA alone and CKD alone patients. Methods: This study included 3207 SpA patients registered in the HURBIO database and treated with bDMARD by August 2023. Of these patients, 34 (1.04%) had CKD (Group 1). Age and sex matced 68 (2.1%) SpA patients without CKD (group 2) were selected for comparasion. Patients were classified according to the Modified New York and the Assessment of SpondyloArthritis International Society criteria. Forty-two patients with CKD (non-SpA) matched for age, sex and GFR (group 3) selected from the nephrology outpatient clinic. Patients with cervical/lumbar stabilization and implants, psoriasis and diffuse idiopathic skeletal hyperostosis (n=4) were excluded. CKD (non-SpA) patients were questioned about inflammatory symptoms, and lumbar, cervical (lateral and antero-posterior (AP)) and pelvic X-rays were evaluated. Demographic characteristics, disease activity (ASDAS-CRP) and functions (BASFI), extra-articular involvements, presence of amyloidosis, and comorbid diseases were assessed. The factors associated with CKD status on univariate analysis with significance at the 0.20 level were entered into a multivariable model. Backward elimination method was used at a significance of 0.05 level. Glomerular filtration rate (GFR) was calculated with the MDRD (modified Modification of Diet in Renal Disease) formula, including the patients' creatine value, age, and gender parameters. CKD was defined as patients with a GFR level below 60 ml/min or GFR level above 60 ml/min and proteinuria above 500 mg/day that persists for more than three months. Radiological evaluation was done by two rheumatologists (U.K. and L.K.) with more than 10 years of experience. Cervical/lumbar AP-lateral and pelvic X-rays were evaluated for erosion, squaring, sclerosis, syndesmophyte (any), bamboo spine, mSASSS, and BASRI scores. Osteoproliferative structural changes in the spine of Group 3 patients were defined as syndesmophyte-like osteoproliferation. Results: When SpA patients with and without CKD were compared, SpA-CKD patients had longer SpA symptoms and disease duration, familial Mediterranean fever (FMF), amyloidosis, radiographic damage (syndesmophytes 64.2% vs. 19.4%) and hip involvement (61.9% vs. 15.2%) were more common in SpA-CKD patients (Table 1). Most (%) SPA-CKD patients were prescribed etanercept, with a 5-year bDMARD retention rate of 45% (log-rank p <0.001). A total of 8/38 (20%) CKD (non-SPA) patients had syndesmophyte-like osteoproliferation (n=5/8 (62.5%) marginal, n=3/8 (37.5%) non-marginal). When CKD (non-SPA) patients were compared with SpA-only patients in group 3, there was no statistically significant difference in the presence of syndesmophytes and median mSASSS scores between the two groups (p>0.05 for all) (Table 2). Conclusion: Osteoproliferative changes in the axial spine are more common in SpA patients with CKD. On the other hand, one-fifth of CKD patients without SpA had syndesmophyte-like osteoproliferation. There is a significant increase in the mSASSS score in SpA patients with CKD. CKD appears to contribute to osteoproliferation independently of SpA. In the presence of CKD accompanying SpA, the contribution of CKD to new bone formation should be taken into consideration in the radiologic evaluation of the axial system. REFERENCES: [1] Nakamura A, Towheed T: Pathogenesis, assessment, and management of bone loss in axial spondyloarthritis. Semin Arthritis Rheum 2024, 64:152345. Acknowledgements: NIL. Disclosure of Interests: None declared.