We assessed the clinical utility of the assay in pediatric patients who (i) developed transplant‐associated thrombotic microangiopathy (TA‐TMA), (ii) have low ADAMTS13 activity, and (iii) develop acquired von Willebrand disease due to extracorporeal membrane oxygenation (ECMO) support. This evidence concerns the gene ADAMTS13 and thrombotic microangiopathy.