Incidence and predictors of severe infections in ANCA-associated vasculitis: a population-based cohort study.

Objective. To determine the incidence rate, predictors and outcome of severe infections in a population-based cohort of ANCA-associated vasculitis (AAV). Methods. The study included 325 cases of AAV (152 female) diagnosed from 1997 through 2016 from a defined geographic area in Sweden. All severe infection events (requiring hospitalization and treatment with intravenous antimicrobials) were identified. The Birmingham vasculitis activity score (BVAS) was used to evaluate disease activity, and organ damage was assessed using the vasculitis damage index (VDI). Patients were followed from time of AAV diagnosis to death or December 2017. Results. A total of 129 (40%) patients suffered at least one severe infection. In 2307 person-years (PY) of followup, 210 severe infections were diagnosed. The incidence rate of severe infections was 9.1/100 PY and was highest during the first year following AAV diagnosis at 22.1/100 PY (P<0.001). Pneumonia, sepsis and urinary tract infection were the most common infections. Opportunistic infections constituted only 6% of all severe infections. In Cox regression analysis age and BVAS at diagnosis were the only factors independently predicting severe infection [hazard ratio: 1.54 (P<0.001) and 1.27 (P¼0.001), respectively]. Severe infection was associated with poorer prognosis with respect to median VDI score 12 months post-AAV diagnosis, renal survival and mortality. Severe infections were the cause of death in 32 patients (22% of all deaths). Conclusion. Severe infection is a common problem in AAV, with the most important prognostic factors being older age and high disease activity at diagnosis. Severe infections are associated with permanent organ damage and high mortality.