title: A plasma protein C activity assay suitable for a clinical laboratory. Its use to measure activity in hereditary and acquired deficiency states.
abstract: The authors describe the technic and standardization of an assay to measure plasma protein C activity feasible for clinical laboratory use. It is modified from an assay of Francis and Patch (Thromb Res 1983; 32:605-613) to enhance protein C recovery in the barium citrate eluate, to eliminate the steps of addition and neutralization of heparin, and to use only commercially available reagents. The normal range for plasma protein C in the assay is 72-130% (+/- 2 SD) (0.7-1.30). Hepatocellular disease lengthening the prothrombin time by 3-4 seconds was associated with plasma protein C activity of 25% (0.25) to 35% (0.35). Although the assay is thought to accurately measure protein C activity in patients taking warfarin, one cannot evaluate such patients for hereditary functional protein C deficiency because treatment with warfarin will itself reduce the ratio of protein C activity to antigen. The assay can be used in a patient receiving heparin if the heparin is removed as described.
mesh_terms: D000990:Antithrombin III; D002951:Citrates; D019343:Citric Acid; D006801:Humans; D008107:Liver Diseases / Q000097:blood; D010314:Partial Thromboplastin Time; D011486:Protein C / Q000032:analysis*; D020151:Protein C Deficiency; D012016:Reference Values; D013917:Thrombin; D013927:Thrombosis / Q000097:blood* / Q000235:genetics; D014859:Warfarin / Q000627:therapeutic use
chemical_list: D002951:Citrates; D011486:Protein C; D019343:Citric Acid; D014859:Warfarin; D000990:Antithrombin III; D013917:Thrombin