Background/Purpose: Antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitides (AAV) are rare yet severe autoimmune diseases. Previous studies have indicated that patients with AAV have an increased risk of venous thromboembolism (VTE) including deep vein thrombosis (DVT) and pulmonary embolism (PE). However, it remains unclear whether the risk is increased equally in granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA), and across both sexes. Therefore, the aim of this study was to assess the risk and timing of VTE events in men and women with GPA and MPA, respectively.

Methods: In a nationwide case-control study, all patients >18 years old with incident GPA or MPA between January 1, 2005, and December 31, 2020, where identified from the National Patient Registers (NPRs) in Sweden. For each patient, five population controls matched for sex and age were selected from the Statistics Sweden Register of Total Population. Primary outcomes were DVT and PE following av AAV diagnosis, identified in the NPRs using ICD codes. Hazard ratios (HRs) of the primary outcomes were calculated using Cox models stratified for AAV subtype and sex, with complete follow-up time or censored after one year and 90 days follow-up post AAV diagnosis, respectively.

Results: In total, 4317 patients (3159 with GPA and 1158 with MPA and 21582 population controls were included in the study. There was no significant difference in risk of VTE between patients with GPA and MPA. Both GPA and MPA were associated with a more than three-fold increased risk of DVT and PE during the entire follow-up time, compared to population controls. This risk was increased to more than 11-fold when follow-up time was censored after one year and more than 20-fold when censored after 90 days (HR (95% confidence interval); HR 21.30 (10.67-42.52)) and PE (HR 22.84 (13.04-40.02)). In sex-stratified analyses, men with GPA and MPA, respectively, exhibited a more than four-fold increased risk of DVT (HR 4.15 (3.07-5.61); 3.49 (2.01-6.06)) and PE (HR 4.68 (3.61-6.06); HR 4.01 (2.47-6.51)). Similarly, women with GPA and MPA, respectively, showed a more than three-fold increased risk of DVT (HR 3.22 (2.28-4.55); HR 4.51 (2.56-7.92)) and PE (HR 3.24 (2.43-4.31); HR 3.54 (2.30- 5.45)). Adjusting for kidney disease had only modest effects on HRs across all comparisons.

Conclusion: Both patients with GPA and MPA exhibit an increased risk of DVT and PE following diagnosis of AAV. Our study did not reveal any significant sex differences in VTE among patients with AAV. This study highlights the importance of being aware of the risk for thromboembolic events, in particular during the first year following an AAV diagnosis.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/incidence-of-venous-thromboembolism-in-patients-with-anca-associated-vasculitides-a-nationwide-registry-based-study-from-sweden/