CPT® Code 85245

The CPT® Code 85245 refers to a laboratory test that measures the levels of factor VIII, von Willebrand (VW) factor, and ristocetin cofactor in the blood. Factor VIII, also known as antihemophilic factor, is a crucial protein in the blood coagulation process, playing a significant role in the formation of blood clots. It works in conjunction with von Willebrand factor, which is essential for stabilizing factor VIII and facilitating its procoagulant activity. Von Willebrand factor exists in two distinct forms: one that circulates freely in the plasma and another that is bound to the alpha granules of circulating platelets. The synthesis and release of plasma von Willebrand factor occur in the vascular endothelial cells, while the platelet-bound form is produced by megakaryocytes in the bone marrow. The test for ristocetin cofactor specifically assesses the activity of von Willebrand factor and its effectiveness in promoting blood clot formation in response to vascular injury. This test is particularly important in the initial evaluation of von Willebrand disease, a bleeding disorder characterized by deficiencies in von Willebrand factor. To perform this test, a blood sample is collected through a venipuncture, which is a separately reportable procedure. The analysis is conducted on platelet-poor plasma using a method known as platelet agglutination, which evaluates the interaction between platelets and von Willebrand factor under the influence of ristocetin.