Transfusion Studies in Patients with Familial Antithrombin III (ATIII) Deficiency: Half‐disappearance Time of Infused ATIII and Influence of such Infusion on Platelet Life‐span

S ummary . Two patients with familial ATIII deficiency received infusions of a concentrate of ATIII prepared from human plasma. Serial plasma samples were assayed for their functional and immunological content of ATIII. The rates of disappearance of ATIII activity found in this study suggest that, initially, frequent infusions are necessary to maintain normal levels of ATIII activity in patients with a severe deficiency. In one patient platelet survival did not appear to be influenced by ATIII infusions.