Objective: To compare serious infection risk for systemic lupus erythematosus (SLE) patients starting glucocorticoids (GC), antimalarials (AM), or their combination.
Methods: We conducted a new-user, historical cohort study, Kaiser Permanente Northern California, 1997-2013. Cox proportional hazards analysis was used to calculate adjusted HR and 95% CI.
Results: The study included 3030 patients with SLE followed an average of 4 years. Compared with patients starting AM without GC (9 infections/1461 patient-yrs), the HR for the risk of infection was 3.9 (95% CI 1.7-9.2) for those starting GC ≤ 15 mg/day without AM (14 infections/252 patient-yrs), while it was 0.0 (0 infections/128 patient-yrs) for those starting the combination. We split the 14 patients with a serious infection and with GC < 15 mg/day into 2 groups: < 7.5 and ≥ 7.5-15 mg/day. The HR for < 7.5 mg/day was 4.6 (95% CI 1.8-11.4) and for ≥ 7.5-15 mg/day, 3.1 (95% CI 1.0-9.7). For patients starting GC > 15 mg/day (reflecting more severe SLE), the risk of infection was nearly the same for the combination of GC and AM (9 infections/135 patient-yrs) and GC alone (41 infections/460 patient-yrs), but the combination users had evidence of more severe disease. Patients with SLE had a 6- to 7-fold greater risk of serious infection than the general population.
Conclusion: Our findings suggest that the benefits of AM treatment for SLE may extend to preventing serious infections. Although the study included > 3000 patients, the statistical power to examine GC dosages < 15 mg/day was poor.
Keywords: COHORT STUDIES; ELECTRONIC MEDICAL RECORDS; EPIDEMIOLOGY; INFECTION; SAFETY; SYSTEMIC LUPUS ERYTHEMATOSUS.