Hypercoagulability test strategies in the protein C and protein S pathway

The protein C-protein S pathway is critical in controlling normal clot formation to provide homeostasis between thrombosis and hemorrhage. Abnormalities have been described in which the pathway is altered because factor V cannot be degraded by activated protein C, producing activated protein C resistance. It has been known for nearly two decades that deficiencies in protein C and protein S can result in impaired inhibition of clot formation resulting in increased risk for thrombosis. This article describes the testing strategies associated with the diagnosis of activated protein C resistance, protein C deficiency, and protein S deficiency.