Antiphospholipid antibody positivity and the thrombotic risk in Japanese patients with anti-neutrophil cytoplasmic antibody-associated vasculitis

ABSTRACT Objectives It has been reported that 21.0–51.7% of anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) patients were antiphospholipid antibody (aPL)-positive. However, the clinical significance of aPL positivity in AAV is not fully understood. Methods We retrospectively assessed patients with AAV diagnosed from 2013 to 2020 at our hospital. Positivity of aPL was defined as positivity of anti-cardiolipin antibody, anti-cardiolipin β2 glycoprotein 1 complex antibody, and/or lupus anticoagulant at least one time during the follow-up periods. The thrombotic risk of aPL positivity was examined by multivariate analyses with the Cox regression model. Results A total of 93 patients with a median age of 71.9 years were included in the study. The median follow-up period was 35.4 months. Thirty-one patients (33.3%) were aPL-positive. Twenty-two thrombotic events occurred in 17 patients (18.3%). Thrombotic events occurred more frequently in aPL-positive patients than in aPL-negative patients (P = 0.011). Multivariate analyses with two different models identified aPL positivity as a thrombotic risk factor (hazard ratios 4.302 and 5.956, 95% confidence intervals 1.546–11.968 and 1.940–18.281, respectively). Conclusions The proportion of aPL-positive patients was 33.3%, and aPL positivity increased the thrombotic risk in Japanese patients with AAV.