Clinical application of a functional assay for protein C.
Protein C (PC) is a vitamin K-dependent protein which functions as a physiologic anticoagulant. In the presence of another vitamin K-dependent protein, protein S, the activated form of protein C (APC) will degrade the active cofactors Va and VIIIa. Both hereditary and acquired deficiencies of PC have been associated with a predisposition to thromboembolic events. We have evaluated a commercial assay system (Stac lot Protein C) which utilizes an extract of snake venom (Protac) that directly activates protein C in vitro. Utilizing this assay, normal individuals, patients with hereditary protein C deficiency, patients who were stably anticoagulated with oral anticoagulants, and patients with lupus anticoagulants were evaluated. Significant discrepancies were noted between protein C antigen and protein C functional activity in patients receiving oral anticoagulants. In addition, patients with lupus anticoagulants may have falsely elevated values for functional protein C activity.
D000284:Administration, Oral; D000925:Anticoagulants / Q000008:administration & dosage; D001779:Blood Coagulation Factors / Q000032:analysis / Q000276:immunology; D001780:Blood Coagulation Tests / Q000379:methods; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D005167:Factor VII / Q000032:analysis; D006493:Heparin; D006801:Humans; D016682:Lupus Coagulation Inhibitor; D011486:Protein C / Q000097:blood*; D020151:Protein C Deficiency; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D013379:Substrate Specificity
D000925:Anticoagulants; D001779:Blood Coagulation Factors; D016682:Lupus Coagulation Inhibitor; D011486:Protein C; D011933:Reagent Kits, Diagnostic; D005167:Factor VII; D006493:Heparin