<h3>Background:</h3> Spondyloarthritis (SpA) is an umbrella for a group of heterogeneous chronic inflammatory conditions. Several studies demonstrated that SpA is associated not only with functional impairment and negative impact on quality of life, but also with increasing health-care cost and resource utilization. <h3>Objectives:</h3> The aim of the study is to estimate the prevalence and direct medical costs of SpA patients using administrative health data at country level for the Colombian Health System. <h3>Methods:</h3> This real-world evidence (RWE) study analyzed administrative databases from the Colombian Health System during 2018 including National Claim Database, Drug Price Information System and Affiliate Database (Figure 1). Prevalence, marginal, incremental, and overall attributable costs were determined using validated algorithms with sensitive and specific identification criteria. The performance of the algorithms was forced to a rigorous validation procedure and evaluated with a deterministic sensitivity analysis. Prevalence was assessed on adults with SpA who were affiliated through contributory health system during 2018. Medical costs were assessed from the payer's perspective for the following health services: diagnosis, outpatient and inpatient appointments, emergency, homecare and treatment. Propensity score matching (PSM) and doubly robust estimation were employed to pair patients based on sociodemographic and clinical variables, creating a quasi-experimental sample for estimating the cost-of-illness (COI) for SpA. <h3>Results:</h3> The prevalence estimated for SpA was 0.66% (n=79,775). Using the specific strategy including medication as an inclusion criterion, the prevalence decreased to 0.21% (n=25,727). The overall attributable costs ranged from USD 218,419,996 (n=79,775) to USD 156,532,798 (n=25,727). The attributable costs related to pharmacological treatment was 54.9% and 76.6% in the sensitive and specific groups, respectively. After adjusting for PSM, the marginal cost per year per patient was USD 2,736 to USD 6,083. Each SpA patient charges an incremental cost of USD 1,989 and USD 5,293 on the national healthcare system. Figure 2. <h3>Conclusion:</h3> This study utilizing real-world evidence provides a comprehensive assessment of the national prevalence and the burden imposed by SpA at the national healthcare system. With the reported prevalence, the study highlights the considerable economic impact, revealing overall attributable costs. Notably, pharmacological treatment accounts for a substantial portion of these costs. The findings underscore the relevant need for targeted interventions and policy measures to address the growing health-care cost and resource utilization associated with SpA, ultimately improving both patient outcomes and the sustainability of the National Health System. <h3>REFERENCES:</h3> [1] Kwan YH, et al. Int J Rheum Dis. 2020 Mar;23(3):334-341 <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>