Pos0804 the Impact of First-Line Tumor Necrosis Factor Inhibitor Treatment on Anti-Infective Use in Patients With Axial Spondyloarthritis: A Nationwide Retrospective Cohort Study

Background: Published data on infection risk in patients with axial spondyloarthritis (axSpA) treated with tumor necrosis factor alfa inhibitors (TNFi) is sparse and mainly consists of randomised control pharmaceutical trials focusing foremost on severe infections leading to hospital admission. Therefore, studies regarding outpatient treated infections are needed in patients with axSpA. Objectives: This study aimed to assess the risk of outpatient anti-infective prescriptions in axSpA patients before and after TNFi therapy and determine factors associated with increased risk of anti-infective use in this patient cohort. Methods: This was a retrospective cohort study. Data on all biologic-naive patients with axSpA initiating treatment with a TNFi in 2003-2018 was extracted from ICEBIO, a nationwide registry of biologic therapy in the field of rheumatology in Iceland. Each patient was matched on age, sex and calendar time to five randomly selected individuals from the general population. All filled anti-infective prescriptions two years before and after TNFi initiation were collected from the nationwide Prescription Medicines Registers. Prescriptions for antimycobacterial, anti-HIV, and anti-hepatitis C were excluded from the analysis. Observation time was defined as two years before and after TNFi initiation or until 30 days after TNFi treatment was discontinued. We calculated the incidence rate (IR) per patient-years (py) for filled prescriptions. Poisson exact test was used to calculate the 95% confidence interval and p-value when comparing incidence rates. Poisson linear regression was used to calculate incidence rate ratios (IRR) and determine significant covariates associated with anti-infective prescriptions after TNFi initiation. Results: Our cohort included 378 axSpA patients, with a mean age of 42.9 ± 13.1 years (Table 1). There were 1886 matched comparators. Before TNFi treatment, axSpA patients had higher IR per py of anti-infective prescriptions compared to their comparators (1.12 (95% CI: 1.04-1.20) vs 0.40 (95% CI: 0.38-0.42), p<0.001). Among axSpA patients, the IR per py of overall anti-infectives increased after initiation of TNFi treatment (1.12 (CI: 1.04-1.20) to 1.43 (CI: 1.35-1.52), p<0.001). The increase was significant for antibiotics (1.04 (CI: 0.97-1.12) to 1.29 (CI: 1.21-1.38), p<0.001) and antivirals (0.03 (CI: 0.2-0.04) vs 0.07 CI; 0.06-0.1), p<0.001) (Figure 1). In a subgroup analysis by sex, females compared to males had higher IR per person-years of anti-infective prescriptions before (1.46 (CI: 1.32-1.62 vs 0.94 (CI: 0.86-1.03), p<0.001) and after 1.88 (CI: 1.71-2.06) vs 1.21(CI: 1.1-1.31), p<0.001) TNFi therapy. In the multivariable analysis, prior anti-infective prescriptions, female sex, and HAQ score at treatment initiation and month 18 were strongly associated with increased incidence of anti-infective prescriptions after initiation of TNFi therapy, while age, smoking, and the use of glucocorticoid and methotrexate were not. Conclusion: The rate of anti-infective prescriptions in this observational cohort is higher than the previously reported rate of non-severe infections in axSpA patients. Anti-infective prescriptions among axSpA patients increased after TNFi initiation in contrast to what has been documented in prior studies on severe infections, indicating either an increase in non-severe infections after TNFi initiation or a lower threshold among physicians to prescribe anti-infectives following treatment initiation. Furthermore, axSpA patients were prescribed more anti-infective prescriptions before TNFi treatment compared to the general population, suggesting elevated baseline infection risk. The study highlights the importance of monitoring and addressing non-severe infections in axSpA patients receiving TNFi therapy. REFERENCES: NIL. Acknowledgements: ICEBIO study group. Disclosure of Interests: None declared.