Assessment of hereditary thrombophilia: Performance of protein C (PC) testing

Abstract

Protein C (PC) is a plasma Vitamin K-dependent pro-enzyme protein that is synthesized in the liver. Upon activation, PC regulates the coagulation process by neutralizing the procoagulant activities of factors V and VIII in the presence of the cofactor Protein S. PC is a major regulator of the coagulation process. The clotting based Protein C assay, the protocol described in this chapter, quantitates the amount of functional PC present in the specimen in a proportional fashion based on the prolongation of the Activated Partial Thromboplastin Time (APTT). Other methods for assessing PC are also available, including chromogenic and antigenic assays, but protocols for these assays are not provided.