Platelet Transfusion in Patients With Low <scp>ADAMTS13</scp> ‐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.