Antithrombin III in fresh frozen plasma, cryoprecipitate, and cryoprecipitate-depleted plasma.

Antithrombin III (AT III) is a plasma protein that inhibits several activated procoagulants. Hereditary disease or acquired conditions such as severe hepatic dysfunction, nephrotic syndrome and intravascular coagulation may be associated with reduced levels of AT III. Its replacement may be essential in controlling thrombosis. In order to determine the most effective form of replacement, we compared AT III biological activity and antigen levels in conventionally prepared fresh frozen plasma, cryoprecipitate and cryoprecipitate depleted plasma (CDP). Both the activity and antigen levels were comparable in all three products (approximately 100%) and AT III was not concentrated in cryoprecipitate. These results indicate that conventionally prepared CDP, fresh frozen plasma and cryoprecipitate contain equal quantities volume for volume of AT III. On this basis, all products are equally effective as therapy for AT III deficiency, but CDP and fresh frozen plasma are recommended as convenient sources of this factor.