AB0429 ANTIMICROBIAL USE AND SEVERE INFECTIONS AMONG PsA PATIENTS AFTER INITIATING TNFi TREATMENT: A POPULATION-BASED MATCHED COHORT STUDY

Background: Genetic and environmental factors are involved in the pathogenesis of psoriasis and psoriatic arthritis (PsA), including infections. These patients are also at increased risk of infections, and the risk is multiplex. There is a loss of integrity of the skin barrier because of the skin disease, cellular immunity is altered, and many are treated with immunosuppressants, including TNF inhibitors (TNFi). While treatment with TNFi is generally well tolerated, potential adverse effects include infections. Although the presence of this risk has been demonstrated in prior studies, it is important to continue to monitor and analyze data to understand better the role of both immunosuppressive treatment and disease severity as TNFi become available to more patients, in part due to the lower costs associated with biosimilars. Objectives: To analyze the incidence of antimicrobial use and severe infections among PsA patients before and after initiating TNFi treatment. Methods: Data on PsA patients starting TNFi treatment from January 2005 through December 2018 was extracted from ICEBIO, a population-based registry. Each patient was matched on age, sex, and calendar time to five randomly selected individuals from the general population. All prescriptions for antimicrobials, glucocorticoids, and methotrexate (MTX) two years before and after initiating TNFi treatment were extracted from the Icelandic Prescription Medicines Register and quantified using the number of prescriptions (NP). Finally, the data were linked to the Icelandic Hospital Discharge Register to obtain data on all infections-related hospitalizations, which were used to define severe infections. A paired t-test was used to analyze the mean NP per year and the mean number of severe infections per year at baseline and after initiating TNFi treatment. Cox proportional hazard models were used to calculate hazard ratios (HRs) for antimicrobial prescription or severe infection among PsA patients initiating TNFi treatment vs. comparators. The multivariable models were adjusted for age, gender, and significant variables from the univariate analysis. Results: The study included 399 PsA patients and 1,986 matched comparators. The PsA patients received more prescriptions for all antimicrobials at baseline compared to comparators with a mean NP per year of 1.26 (95% CI 1.10-1.42) vs. 0.60 (95% CI 0.55-0.66), p<0.001. The mean NP per year increased significantly in the first 12 months after initiating TNFi treatment among the PsA patients to 1.64 (95% CI 1.42-1.86) p<0.001 but decreased to the same number as before TNFi after that with a mean NP per year of 1.25 (95% CI 1.04-1.47) after 12-24 months. No significant increase in severe infections was found. When adjusted for covariates, PsA patients had an increased risk of receiving a prescription for antimicrobials compared to comparators, HR 2.52 (95% CI 2.10-3.03, p<0.001). An increased risk of severe infections was not found in the adjusted model. Conclusion: Patients with PsA have a higher incidence of antimicrobial prescription at baseline compared to the general population. The incidence increases in the first year after initiating TNFi treatment but reaches the same level after that. Table 1. Mean number of antimicrobial prescriptions per year before and after initiating TNFi treatment. *p<0.05; **p<0.001 by paired t-test. Abbreviations: TNF = tumor necrosis factor, CI = confidence interval, PsA = psoriatic arthritis. REFERENCES: NIL. Acknowledgements: We thank all the individuals who record their symptoms in ICEBIO along with rheumatologists in Iceland who are part of the ICEBIO group. Also, the authors wish to thank Niels Steen Krogh at ZiteLab ApS for his help in acquiring and cleaning the dataset. Disclosure of Interests: Telma Thrastardóttir: None declared, Aron H Bjornsson: None declared, Alexis Ogdie has served as a consultant for Abbvie, Amgen, BMS, Celgene, Corrona, Global Health Living Foundation, Janssen, Lilly, Novartis, Pfizer, and Takeda, has received grants to the University of Pennsylvania from Pfizer and Novartis and to Forward from Amgen. Her husband has received royalties from Novartis, Bjorn Gudbjornsson: None declared, Thorvardur J Love has received reimbursement from Celgene for speaking about guidelines for the treatment of PsA.