Platelet Transfusion in Patients With Low ADAMTS13 ‐Confirmed Thrombotic Thrombocytopenic Purpura Is Associated With Increased Mortality

Background Thrombotic thrombocytopenic purpura (TTP) is a life‐threatening thrombotic microangiopathy caused by severe ADAMTS13 deficiency. Platelet transfusions are generally contraindicated but are often administered before TTP is recognized. Objectives To evaluate the association between platelet transfusion in the emergency department (ED) and outcomes in laboratory‐confirmed TTP. Methods We conducted a retrospective multicenter cohort study using the TriNetX Research Network (2014–2025). Adults presenting to the ED with ADAMTS13 activity < 10% who received plasma exchange within 48 h were included. The exposure was platelet transfusion within 24 h. The primary outcome was 30‐day all‐cause mortality; secondary outcomes included myocardial infarction (MI), stroke, intracranial hemorrhage, thrombosis, and ICU‐level care. Propensity score matching (1:1) and Cox modeling were performed. Results Among 693 patients, 99 (13.9%) received platelet transfusion. After matching, platelet transfusion was associated with higher 30‐day mortality (30.0% vs. 13.3%; OR 2.79, 95% CI 1.31–5.93; p = 0.008) and increased MI. In Cox analysis, platelet transfusion remained independently associated with mortality (adjusted HR 2.45, 95% CI 1.24–4.85). Conclusions In confirmed TTP, early platelet transfusion was independently associated with increased short‐term mortality, supporting recommendations to avoid platelet transfusion and emphasizing early recognition.