Abstract 14 — Comparison of the ASAS Health Index Between Radiographic Axial Spondyloarthritis and Non-Radiographic Spondyloarthritis in Singapore

Background Prior studies reported conflicting results regarding differences in Assessment of SpondyloArthritis (ASAS) Health Index (HI) scores between radiographic axial spondyloarthritis (r-axSpA) and non-radiographic axial spondyloarthritis (nr-axSpA). Country-level variations in disease activity were also observed. Hence, this study aimed to compare the ASAS HI scores between r-axSpA and nr-axSpA in Singapore, and determine factors associated with poorer ASAS HI scores. Methods This was a cross-sectional evaluation of baseline data from a prospective cohort study in Singapore General Hospital, from January 2018 to March 2023. Patients aged 21 years and above who were clinically diagnosed with axial spondyloarthritis (axSpA) based on the 2009 ASAS criteria were included. Sociodemographic variables, clinical variables and patient-reported outcomes were collected. Univariable and multivariable linear regression were performed to identify variables associated with ASAS HI scores. Variables with p-value of <0.10 were included in the multivariable regression. A p-value of <0.05 was considered significant. Results Of the 331 patients, 265 (80.0%) and 66 (20.0%) had r-axSpA and nr-axSpA respectively. The median (IQR) age in r-axSpA was [40.0 (30.0-53.0) years], higher than nr-axSpA [34.0 (25.0-47.0) years], p<0.01. There was a higher proportion of males in r-axSpA (80.4%) than nr-axSpA (65.2%), p=0.01. Patients with r-axSpA had a longer disease duration [6.8 (1.8-14.0) years] than nr-axSpA [1.1 (0.2-5.4) years], p<0.01. More patients with r-axSpA (90.2%) were positive for HLA-B27 than nr-axSpA (69.7%), p<0.01. Differences in ASAS HI scores were not statistically significant between r-axSpA and nr-axSpA [4.0 (2.0-6.8) vs 5.5 (1.1-8.5), p=0.12]. Post multivariable regression, nr-axSpA ([Formula: see text]: 0.70, 95% CI: 0.09, 1.32, p=0.02), BASDAI ([Formula: see text]: 0.18, 95% CI: 0.01, 0.35, p=0.04), BASFI ([Formula: see text]: 0.47, 95% CI: 0.30, 0.65, p<0.01) and HADS-Depression scores ([Formula: see text]: 0.11, 95% CI: 0.01, 0.21, p=0.04) were positively associated with ASAS HI. Higher SF36-PCS ([Formula: see text]: −0.11, 95% CI: −0.14, −0.08, p<0.01) and SF36-MCS ([Formula: see text]: −0.07, 95% CI: −0.10, −0.04, p<0.01) were negatively associated with ASAS HI (Table 1). Conclusion Patients with nr-axSpA were associated with poorer overall health and functioning as compared to r-axSpA. Higher disease activity, poorer physical function, poorer mental health status and more depressive symptoms were associated with worse health and functioning.