High risk of stroke in ANCA-associated vasculitis—a population-based study

OBJECTIVE: To determine the incidence rate, predictors and outcome of stroke in a population-based cohort of individuals with ANCA-associated vasculitis (AAV). METHODS: The study included 325 patients diagnosed with AAV from 1997 through 2016 in a defined geographic area of Sweden. Patients who suffered a stroke were identified from Riksstroke, a national Swedish stroke register established in 1994, and the Skåne Healthcare Register (SHR), which includes data for all inhabitants of Skåne since 1998. Case record review was carried out to confirm the diagnosis of stroke in AAV patients identified in the SHR. The incidence rate of stroke was calculated per 1000 person-years of follow-up. Using data from the Swedish general population, the standardized incidence ratio (SIR) of stroke was estimated. Cox regression analysis was utilized to investigate survival and predictors of stroke. RESULTS: Twenty-five subjects (8%) suffered a stroke during 2206 person-years of follow-up. The incidence rate of stroke in AAV was 11.3/1000 person-years (95% CI 6.9, 15.8). Patients with AAV showed an increased risk of stroke compared with the general population [SIR 1.85 (95% CI 1.27, 2.59)], with a greater risk for those <65 years of age [SIR 3.19 (95% CI 1.53, 5.88)]. Higher platelet count at AAV diagnosis was an independent predictor of stroke [hazard ratio 1.14 (95% CI 1.00, 1.29)]. There were no differences in survival or other outcome measures between AAV patients with and without stroke. CONCLUSIONS: The incidence rate of stroke in AAV is higher than in the general population. High platelet count at AAV diagnosis was associated with an increased risk of stroke.