AB0949 EVOLVING TRENDS IN ANKYLOSING SPONDYLITIS DIAGNOSIS AND MANAGEMENT: A DECADE-LONG STUDY (2010-2021) USING DATA FROM THE NATIONAL HEALTH INSURANCE SERVICE IN SOUTH KOREA
Authors: S. W. Nam, J. H. Jung
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Ankylosing Spondylitis (AS) is a chronic inflammatory arthritis primarily affecting the axial skeleton, presenting diagnostic and management challenges. Understanding the epidemiological trends and clinical characteristics of AS is crucial for informed decision-making. <h3>Objectives:</h3> To analyze the trends and patterns in diagnosis, clinical characteristics, and management of AS over a decade in South Korea, utilizing the National Health Insurance Service (NHIS) database. <h3>Methods:</h3> This retrospective cohort study utilized data from the Korean NHIS claims database, identifying 31,753 incident AS patients between 2010 and 2021. We calculated age-standardized prevalence and incidence rates, assessed annual incidence trends of AS by age groups, trends in pre-diagnostic sacroiliac (SI) joint magnetic resonance imaging (MRI) utilization, and examined medication usage patterns. We also analyzed the timing of tumor necrosis factor alpha (TNF-α) inhibitor therapy initiation. <h3>Results:</h3> Over the study period, the age-standardized prevalence rate consistently increased, escalating from 34.6 (95% CI: 34.0 – 35.2) per 100,000 individuals in 2010 to 86.4 (95% CI: 85.6 – 87.3) per 100,000 individuals in 2021. The age-standardized incidence rate also demonstrated year-over-year growth, rising from 4.41 (95% CI: 4.20 – 4.61) per 100,000 person-years in 2010 to 7.63 (95% CI: 7.38 – 7.89) per 100,000 person-years in 2021. The most substantial rise in incidence was observed among younger age groups (Figure 2). Clinical characteristics of patients with incident diagnosis of AS from 2010 to 2021 were evaluated. The mean age at diagnosis was 39.7 ± 15.2, which was higher in females (43.1 ± 15.9 vs. 38.5 ± 14.8 in males, p &lt; 0.001). The male to female ratio was approximately 2.87:1. Uveitis was the most common extra-articular manifestation of AS, occurring in 31.1% of patients, with a higher prevalence in females (33.1% vs. 30.5% in males, p &lt; 0.001). EAMs including uveitis, psoriasis, and ulcerative colitis were more common in female patients (p &lt; 0.05). The percentage of patients who had an SI joint MRI within three months before diagnosis among those newly diagnosed with AS rose from 5.68% in 2011 to 11.9% in 2021 (p for trend &lt; 0.001). Nonsteroidal anti-inflammatory drugs (NSAIDs) were the most frequently prescribed medications (94.8%), while TNF-α inhibitors were used in 31.2% of AS patients. Interleukin-17 inhibitors were approved as second-line biologic therapies after TNF-α inhibitors for reimbursement indication of AS in 2020, and 1.1% of AS patients used them. Notably, 17.4% of newly diagnosed AS patients initiated TNF-α inhibitors within six months after diagnosis, consistently surpassing the rates of those who started treatment between 6 months to 2 years post-diagnosis. <h3>Conclusion:</h3> This study highlights the growing burden of AS in South Korea, particularly among young individuals. Increasing pre-diagnostic MRI use and early TNF-α inhibitor initiation signify progress in AS diagnosis and management. These findings emphasize the importance of continued research and early intervention to improve patient outcomes and reduce the societal impact of AS. <h3>REFERENCES:</h3> <b>NIL.</b> <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>