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

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.