Op0103 Comorbidity Burden and Radiographic Progression in Axial Spondyloarthritis

Background: Comorbidity burden (the number of comorbidities) is associated with greater disease activity and reduced treatment response among people with axial spondyloarthritis (axSpA), but whether it is associated with radiographic progression remains unclear. Objectives: To examine the association between comorbidity burden and radiographic progression in radiographic-axSpA. Methods: We used clinical and radiographic data from the Australo-Anglo-American Spondyloarthritis Consortium (TASC). Comorbidity burden was defined as a count of 22 conditions. Radiographs were scored using a modified version of mSASSS (original mSASSS scores of ≥1 minus 1) to reduce ambiguity between scores of 0 and 1 [1]. For C-spine, missing vertebra scores were replaced with the mean if <4 were missing; the same was applied to L-spine. Total mSASSS was invalidated if ≥4 scores were missing in either C- or L-spine. Baseline was defined as date of the first radiograph. We used generalized estimating equations with mSASSS as outcome, and baseline comorbidity count (0, 1, 2, ≥3), time (years) and comorbidity-time-interaction as independent variables, to assess whether change in mSASSS over time differed between groups. Primary analyses used complete cases adjusting for baseline covariates: mSASSS, gender, symptom duration, CRP, TNFi use (yes, no, missing), number of extra-musculoskeletal manifestations (uveitis, psoriasis, IBD) and smoking status (never, previous, current). HLA-B27 was not included as a covariate because it was not associated with progression. Models were repeated using ASDAS instead of CRP and using multiple imputation for missing covariates. Results: Analyses included 1,150 individuals (mean age 44 (14) years, 75% male, 84% HLA-B27 positive) over 3,441 patient-years (median follow-up 2.0 years, median 2 (IQR1, 3) radiographs). Among 81% with available baseline data, 38% were on a TNFi. 679 (27%) had no comorbidities, 655 (26%) had one, 567 (22%) two, 636 (25%) three comorbidities; median number of comorbidities was 1 (range 0-10). Figure 1 shows the prevalence of each comorbidity. Compared to those without comorbidities, the group with any comorbidities were older, more often ever smokers, had higher mean baseline mSASSS and ASDAS, but comparable CRP (Table 1). Increase in mSASSS over time was greater with increasing comorbidity burden (Figure 1). Compared to those without comorbidities, having one comorbidity was not associated with change in mSASSS (-0.2 mSASSS units over 10 years on average; 95%CI -1.0, 0.6; p=0.652), but having two (2.7 units/10 years; 95%CI 2.0, 3.5; p<0.001) and three or more (2.3 units/10 years; 95%CI 1.5, 3.1; p<0.001) were. Associations were not driven by one single comorbidity. Results were similar when using ASDAS instead of CRP, or when using multiple imputation for missing covariates. Conclusion: Increasing comorbidity burden is independently associated with greater radiographic progression. Further research is needed to identify which conditions contribute disproportionately to, and causal mechanisms to explain, these observed associations. REFERENCES: [1] Cortes A. Ann Rheum Dis 2015;74:1387–93. Table 1. Baseline characteristics of individuals with axial spondyloarthritis with and without comorbidities. Acknowledgements: NIL. Disclosure of Interests: Sizheng Steven Zhao UCB, Novartis, Abbvie, UCB, Nicholas Harvey: None declared, Linda A Bradbury: None declared, Lianne S Gensler Acelyrin, Janssen, Novartis, Pfizer, UCB, Novartis, UCB, Zhixiu Li: None declared, Mohammad Rahbar: None declared, Michael M Ward: None declared, Michael H Weisman: None declared, John D Reveille: None declared, Tae-Hwan Kim: None declared, Matthew Brown Novartis, UCB, Clementia, Incyte, Ipsen, UCB, Xinthera, UCB.