Diabetes mellitus and cardiac disease as key predictors of rituximab-induced acute thrombocytopenia in ANCA-associated vasculitis

Objectives Rituximab (RTX) is a key treatment for ANCA-associated vasculitis (AAV), but RTX-induced acute thrombocytopenia (RIAT) remains a concern. We aimed to evaluate the risk and risk factors of RIAT in patients with AAV undergoing RTX induction therapy. Methods Patients with new-onset microscopic polyangiitis or granulomatosis with polyangiitis who received RTX in a nationwide multicentre registry in Japan were included. RIAT was defined by platelet count reductions within 28 days post-RTX. Risk factors for RIAT were identified by using logistic regression with stepwise selection, and prediction models were developed. Model performance was assessed using c-statistics. Results Among 175 patients with AAV receiving RTX, RIAT occurred in 35.4% of them. Diabetes mellitus (odds ratio [OR] = 4.96), cardiac disease (OR = 3.57), low platelet count (OR = 1.04 per 104/μL decrease), increased serum creatinine (OR = 1.44 per 1 mg/dl increase), low albumin (OR = 2.33 per 1 g/dl decrease), and high KL-6 (OR = 1.09 per 100 U/ml increase) were identified as significant predictors. A predictive model incorporating these factors achieved a C-statistic of 0.817. Conclusion RIAT is a frequent complication of RTX induction in patients with AAV, with diabetes mellitus and cardiac disease being strong risk factors. Our predictive model would enables risk assessment for RIAT, allowing clinicians to optimize treatment strategies.