Background Patients with RA undergoing major surgery are at high risk for infection. Different biologic DMARDs may be associated with different infection risks.1
Objectives Goals were 1) to compare post-operative infection risk after arthroplasty in patients with RA exposed to different biologics, and 2) examine associations between glucocorticoid use and post-operative infection.
Methods A retrospective cohort study using U.S. Medicare data from 2006-September 2015 evaluated adults with ≥2 ICD9 codes for RA undergoing elective inpatient primary or revision total knee or hip arthroplasty. Eligible patients received an infusion or prescription for abatacept, adalimumab, etanercept, infliximab, or tocilizumab within 8 weeks or a rituximab infusion within 16 weeks of surgery. Patients with hip fracture, malignancy, pre-existing infection, or non-elective surgery were excluded. Average glucocorticoid dose in the 3 months before surgery was calculated from oral prescriptions. Logistic or Cox regression evaluated associations between biologic exposure and post-operative outcomes: 1) hospitalised infection within 30 days (from discharge diagnoses, PPV >80%), 2) rate of prosthetic joint infection (PJI, ICD9 996.66) within 1 year, and 3) 30 day readmission among patients with discharge to home, skilled nursing facility, or inpatient rehab. Propensity scores based on the probability of receiving a specific biologic treatment were used to balance confounders across treatment groups using inverse probability weighting. Similar analyses were used to evaluate associations between glucocorticoid dose and outcomes in the same cohort, using inverse probability weighted analyses based on the probability of being in each glucocorticoid treatment category.
Results Among 7929 surgeries in 7138 patients, there were 717 (9.0%) hospitalised infections within 30 days of surgery (most commonly urinary, skin/soft tissue, and pneumonia), 192 (2.8/100 person-years) PJI within 1 year, and 465/7554 (6.2%) 30 day readmissions. There was no significant difference in the risk of hospitalised infection, PJI, or 30 day readmission across biologic treatment groups (table 1). Glucocorticoid dose >10 mg/day (mean 13.5±3.5 mg/day) was associated with a significantly greater risk of hospitalised infection [aOR 2.37 (1.63–3.44)] and prosthetic joint infection [aHR 2.04 (1.09–3.84)] compared to no glucocorticoid use (table 1). Patients with glucocorticoid dose >10 mg also had a numerically greater risk of 30 day readmission that did not reach statistical significance [aOR 1.61 (0.99–2.61)] (table 1).
Conclusions Risk of hospitalised infection, prosthetic joint infection, and readmission after arthroplasty was similar in patients with RA treated with different biologics. In contrast, glucocorticoid use, especially >10 mg/day, was associated with greater risk of hospitalised infection and PJI.
Reference  Yun H, et al. Comparative risk of hospitalized infection associated with biologic agents in rheumatoid arthritis patients enrolled in medicare. Arthritis & Rheumatology2016;68:56–66.
Disclosure of Interest M. George Grant/research support from: Bristol Myers Squibb, J. Baker: None declared, K. Winthrop Grant/research support from: Abbvie, Astellis, Galapagos, Eli Lilly, Pfizer, BMS, Roche, UCB, Consultant for: Abbvie, Astellis, Galapagos, Eli Lilly, Pfizer, BMS, Roche, UCB, E. Alemao Employee of: Bristol Myers Squibb, L. Chen: None declared, S. Connolly Employee of: Bristol Myers Squibb, T. Simon Employee of: Bristol Myers Squibb, Q. Wu: None declared, F. Xie: None declared, S. Yang: None declared, J. Curtis Grant/research support from: Pfizer, Amgen, UCB, Myriad genetics, Bristol Myers Squibb, Consultant for: Pfizer, Amgen, UCB, Myriad genetics, Bristol Myers Squibb, Janssen
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