The aims of this study were to define the risk of serious bacterial infections in patients receiving specific biological disease-modifying anti-rheumatic drugs (bDMARDs) and evaluating the effect of concomitant synthetic DMARDs (sDMARDs) in a large population-based sample of rheumatoid arthritis (RA) deriving from an administrative health database.
Data were extracted from health databases of Lombardy Region, Italy (2004-2013), as a part of the RECord-linkage On Rheumatic Diseases (RECORD) study. Patients with RA treated with approved bDMARDs were included. Hospitalisations for bacterial infections were evaluated by hospital discharge forms. The association between drug exposure and infections was assessed by survival models, with time-dependent covariates. Results are presented as hazard ratios (HR) and 95%CI, crude and adjusted for pre-specified confounders (sex, age, disease duration, Charlson Comorbidity Index, previous biologics, previous infections, use of methotrexate, leflunomide, corticosteroids, non-steroidal anti-inflammatory drugs).
4,656 RA patients with at least one bDMARD prescription were included, for a total of 7,601 biological courses; 3,603 (77.4%) women with a mean (SD) age of 55.8 (12.7) years. Crude incidence rate of hospitalised infection ranged from 0.14 to 2.95 per 1000 person-years. After multivariable adjustment, abatacept users (HR 0.29, 95%CI 0.10-0.82) had significantly lower risk of infections compared to etanercept. Concurrent treatment with methotrexate (0.72, 0.52-0.99) reduced the overall risk of infection while glucocorticoids increased it (1.09 per mg/day, 1.06-1.11).
In RA patients treated with bDMARDs, abatacept was associated with the lowest risk of infections; overall risk was mitigated by concomitant methotrexate and increased by glucocorticoids in a dose-dependent manner.