A new method for the estimation of protein C by ELISA

A new solid phase enzyme-linked immunosorbent assay (ELISA) was developed for the quantitation of human protein C antigen. Anti-protein C F(ab')2 fragments were adsorbed to polystyrene plates. The binding of serial dilutions of control or test plasma, containing protein C, was detected by incubation with peroxidase-labeled anti-protein. C-IgG followed by the addition of hydrogen peroxyde and 0-phenylenediamine. This ELISA is specific, sensitive (detection limit: 0.02%) and accurate (variation coefficient: 3 to 10%). When results are compared to those obtained by the Laurell technique (electroimmunodiffusion, EID), the correlation coefficient is 0.95 in all tested plasmas. Protein C antigen was measured by ELISA and EID in plasma from 40 controls, 14 patients with congenital protein C deficiency, 15 patients with liver cirrhosis and 40 dicoumarol-treated cases. In normal plasma, protein C ranged from 70 to 126%. In congenital deficiency, protein C was between 35 and 58% in 13 cases and 9% in one of them. In patients with liver cirrhosis and dicoumarol-treated cases, levels of protein C antigen were compared to those of other vitamin K dependent factors, i.e. Factors II and IX measured by EID and Factor X assayed by EID and ELISA. In liver cirrhosis, the amount of protein C was significantly lower than that of Factors II, IX and X. In short-term and long-term dicoumarol-treated patients, the highest correlation (r = 0.72) was observed between protein C and Factor X levels. In the plasma of patients undergoing oral anticoagulant therapy, protein C decreased more rapidly than Factors X or II and migrated in presence of calcium as a double peak, one with a normal mobility and one more anodal corresponding to the non carboxylated form of protein C.

[The factor VIII complex: hemophilia A and von Willebrand disease]

The factor VIII complex is a macromolecule with two distinct components. One is the coagulation factor VIII. The other, known as the Willebrand factor, is a polymer which probably acts as a carrier for serum factor VIII. Hereditary disorders can affect either of these two components. Hemophilia A is a coagulation disorders due to decreased factor VIII coagulant activity. Increase of partial activated thromboplastin time parallels disease severity. Hematomas and hemarthrosis in large joints are the main clinical features. In von Willebrand disease, mucocutaneous bleeding is the main symptom. Diagnosis is established by demonstrating disorders of primary hemostasis: prolonged bleeding time and decreased ristocetin-induced platelet aggregation. Two forms of von Willebrand disease have been described. In the quantitative form, decreased synthesis of von Willebrand factor is often responsible for severe clinical manifestations. The qualitative form probably results from defective polymerization of von Willebrand factor subunits. In both these forms, deficient primary hemostasis is a consequence of decreased platelet adhesion to the vascular wall. Clinical and biological features of hemophilia A and von Willebrand disease, as well as their management, are discussed.