Risk of Serious Infection With Low-dose Glucocorticoids in Patients With Rheumatoid Arthritis: An Instrumental Variable Analysis

Abstract

Background: Low-dose glucocorticoids are commonly used in the treatment of rheumatoid arthritis (RA). Observational studies have found an increased risk of serious infection associated with low-dose glucocorticoids, but concerns about residual confounding remain.

Methods: We identified adults with RA on stable immunomodulatory therapy for >6 months receiving no glucocorticoids or ≤5 mg/day using Medicare data from 2006 to 2015. We used provider preference for glucocorticoids as an instrumental variable (IV) to assess associations between low-dose glucocorticoid use and the risk of infection requiring hospitalization using a cause-specific proportional hazards model.

Results: We identified 163,603 qualifying treatment episodes among 120,656 patients. Glucocorticoids ≤5 mg/day were used by 25,373/81,802 (31.0%) of patients seen by a rheumatologist with low provider preference for glucocorticoids and by 36,087/81,801 (44.1%) of patients seen by a rheumatologist with high provider preference for glucocorticoids (adjusted odds ratio 1.81, 95% confidence interval 1.77, 1.84 for association between provider preference and glucocorticoids). Chronic obstructive pulmonary disease, opioids, antibiotics, previous emergency department visits, hospitalizations, and infections requiring hospitalization infections were unbalanced with regard to exposure but not to the IV. The incidence of infection requiring hospitalization was 8.0/100 person-years among patients unexposed to glucocorticoids versus 11.7/100 person-years among those exposed. The association between glucocorticoids and infection requiring hospitalization from IV analysis (hazard ratio 1.26 [1.02-1.56]) was similar to results from a standard multivariable model (hazard ratio 1.24 [1.21-1.28]).

Conclusions: Among patients with RA on stable immunomodulatory therapy, IV analysis based on provider preference demonstrated an increased risk of infection requiring hospitalization associated with low-dose glucocorticoids, similar to a traditional analysis.