Protein C Antigen Test Kit

Protein C is a vitamin K-dependent protein synthesized primarily by hepatocytes in the liver and plays an important physiologic role in the Protein C Anticoagulant System.1,2 Protein C, thrombin from blood clots, and endothelial cells, through complex interactions with other factors of the coagulation cascade, contribute to the maintenance of normal hemostatic mechanisms by down-regulating clot formation and by promoting fibrinolysis. The Protein C Anticoagulant System is activated by the binding of thrombin to thrombomodulin, a transmembrane protein receptor on endothelial cells.3 The thrombin-thrombomodulin binding on endothelial cell membranes activates circulating Protein C. Activated Protein C binds to Protein S on the membrane of endothelial cells or platelets. In this Protein C-Protein S complex, activated Protein C is now capable of inactivating coagulation factors Va and VIIIa, down-regulating clot formation. Activated Protein C also enhances the function of tissue plasminogen activator (TPA) by dissociating this molecule from its inhibitor, plasminogen activator inhibitor-1 (PAI-1), thereby facilitating clot dissolution or fibrinolysis.1-3

Protein C deficiency, either congenital or acquired, may lead to serious thrombotic events such as thrombophlebitis, deep vein thrombosis, or pulmonary embolism.4 Patients with a congenital heterozygous deficiency may present with venous thrombosis in young adulthood, while patients with the rare homozygous deficiency present with massive thrombosis (purpura fulminans) during the neonatal period.5 The prevalence of Protein C deficiency in the general population has been estimated at 1 in 300. In younger patients (<40-45 years) with recurrent venous thrombosis, the frequency of Protein C deficiencies may be as high as 10 to 15%.6-7 Acquired Protein C deficiency may be seen in liver disease, extensive thrombotic episodes, surgery, oral anticoagulant therapy, antiphospholipid syndrome, etc. A decreased Protein C activity in plasma may be the result of low concentrations and function (type I) or only low function (type II).6

The laboratory diagnosis of Protein C deficiency may require both quantitative and qualitative (functional) determinations. Quantitative determinations of Protein C Antigen are based on immunologic procedures such as radial immunodiffusion in gel, Laurell rocket immunoelectrophoresis and enzyme-linked immunosorbent assay (ELISA).6,8 ELISA procedures are less labor intensive and offer several advantages including more objective, accurate and reproducible results. In addition, ELISA allows automation with commonly available laboratory instruments.