DIC needs to be differentiated from various other medical conditions. Prolongation of the prothrombin and partial thromboplastin times, thrombocytopenia, hypofibrinogenemia, and a raised level of fibrin degradation products all may occur in liver disease; in difficult cases, assay of factor VIIIc may be helpful (low in DIC but normal or raised in liver disease). Critically ill patients may develop a coagulopathy due to vitamin K deficiency; a therapeutic trial of the vitamin may clarify whether such a deficiency is present. Widespread thromboses, multiorgan dysfunction, thrombocytopenia, and microangiopathic hemolysis all occur in thrombotic thrombocytopenic purpura; however, major coagulation abnormalities are uncommon in this disorder. Finally, a raised level of fibrin degradation products may be found after major thrombosis, thrombolytic therapy, and major surgery, although this seldom creates major diagnostic difficulty.