AB0920 BAMBOO SPINE PHENOTYPE ASSOCIATED WITH A HIGHER DISEASE BURDEN IN SPONDYLOARTHRITIS PATIENTS: AN ANCILLARY ANALYSIS OF THE ASAS-COMOSPA STUDY
Authors: S. Hamroun, C. López-Medina, A. Etcheto, K. Oh, M. Dougados, A. Moltó, C. Miceli Richard, O. Fogel
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> The severity of spondyloarthritis (SpA) is intricately connected to its structural damage, but little is known about its more severe form, the Bamboo Spine phenotype<sup>1</sup>. <h3>Objectives:</h3> This study aimed to assess the clinical and paraclinical characteristics, as well as the comorbidities in SpA patients with the Bamboo Spine phenotype. <h3>Methods:</h3> Data from the ASAS COMOrbidities in SPondyloarthritis (ASAS-COMOSPA) study were used. ASAS-COMOSPA is a multinational, cross-sectional study including consecutive diagnosed SpA patents by rheumatologists worldwide. A descriptive analysis of the population was carried out, according to the Bamboo Spine phenotype (as determined by rheumatologists). Multivariate logistic regression was performed following the selection of explanatory variables from univariate analyses (p &lt; 0.2). To address missing data among explanatory variables, multiple imputation (using mice) was applied. The geographical origin of patients was treated as a binary variable, distinguishing high- and middle-income countries from low-income countries, according to WHO classification. <h3>Results:</h3> Of the 3984 patients included in the ASAS-COMOSPA study, 3943 were analysed after excluding cases with unknown Bamboo Spine status. Among these, 275 (6.97%) had a Bamboo Spine phenotype, displaying interregional variability (ranging from 1.2% in North America to 16.9% in North Africa). Univariate analyses revealed associations between the Bamboo Spine phenotype and male sex, smoking, age, disease duration, HLA B27 positivity, increased CRP, BASFI score, history of hip arthroplasty, osteoporosis, renal insufficiency, hypertension, digestive ulcer, and exposure to NSAIDs (Table 1). Conversely, psoriasis, peripheral involvement, BASDAI score and exposure to TNF inhibitors were associated with the absence of the Bamboo Spine phenotype. The multivariate model, adjusted for all these variables, demonstrated a loss of significance in the association with the Bamboo Spine phenotype for renal insufficiency, hypertension, and exposure to TNF inhibitors. <h3>Conclusion:</h3> The prevalence of the Bamboo Spine phenotype in this study was 6.97%, which remains significant in the biologic's era. Patients with the Bamboo Spine phenotype have a greater disease burden, as evidenced by a higher BASFI score, more frequent hip arthroplasty, but also an increased risk of comorbidities, some of which appear linked to long-term exposure to NSAIDs. These findings underscore the importance of early detection of these comorbidities, and improved access to biologics considering the potential adverse effects of prolonged NSAIDs exposure in these patients. <b>Table 1.</b> Clinical, paraclinical characteristics and comorbidities of patients, according to the Bamboo Spine phenotype. <b>Table 2.</b> Factors associated with the Bamboo Spine phenotype. <h3>REFERENCES:</h3> [1] Atagündüz P. Clin Exp Rheumatol. 20223 Mar;41(3):620-627 <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>