Hemostatic enzyme generation in the blood of patients with hereditary protein C deficiency

Abstract

The presence of hereditary protein C deficiency has been shown to predispose patients to the development of venous thrombosis. We used radioimmunoassays for the protein C activation peptide (PCP) and the prothrombin fragment F1 + 2 to quantitate the extent of in vivo activation of protein C by thrombin-thrombomodulin and prothrombin by factor Xa, respectively, in the blood of individuals with this clinical disorder. A total of 46 protein C deficient subjects from 18 kindreds were studied. In 23 nonanticoagulated patients with an isolated deficiency of protein C, the mean level of PCP was substantially reduced while the mean concentration of F1 + 2 was significantly elevated as compared with normal controls (1.10 pmol/L v 1.78 pmol/L, P less than .0005 and 2.54 nmol/L v 1.51 nmol/L, P less than .0005, respectively). The metabolic behavior of 131I-F1 + 2 was found to be similar in protein C deficient patients and normal individuals. However, we were unable to establish a significant correlation between decreased PCP levels and increased F1 + 2 measurements in these 23 patients. This study demonstrates that heterozygous protein C deficient individuals with equivalent plasma levels of the zymogen may have markedly different biochemical profiles when assay techniques are used that quantitate the in vivo activity of the coagulation system. Six individuals from three pedigrees were identified as having combined deficiencies of protein C and either antithrombin III or protein S; the genetic basis for the combined deficiency state was determined in two of the kindreds. Finally we observed that hemostatic system activity as measured by the PCP and F1 + 2 assays is markedly suppressed in protein C deficient patients who are chronically anticoagulated with coumarin derivatives.

Heritability of plasma concentrations of clotting factors and measures of a prethrombotic state in a protein C‐deficient family

“…All assays were performed in the investigators' laboratories either by ELISA: FV antigen [coefficient of variation (CV) 5.8%][21], FVIII antigen (CV 7.8%), FIX antigen (CV 10%), VWF (CV 3%) [22], protein Z (CV 6.5%) [24], ZPI (CV 7.2%) [24], APC–α1AT complex (CV 12.4%) [25] and APC–PCI complex (CV 11.7%) [25], or radioimmunoassay: prothrombin (CV 8%) [26], antithrombin (CV 5%) [27,28], protein S (CV 9.8%) [29], F1.2 (CV 8%) [28], PCP (CV 14%) [28] and FPA (CV 8%) [28], the Clauss method for fibrinogen (CV 1.7%) [30,31] using the ST4 instrument (Diagnostica Stago, Parsipanny, NJ, USA), a clot‐based functional assay for protein C: (CV 5.5%) [20,23] or micro latex bead agglutination for d ‐dimer (CV 9.2%) (Biomerieux, Durham, NC, USA) [32,33].…”

Combinations of 4 mutations (FV R506Q, FV H1299R, FV Y1702C, PT 20210G/A) affecting the prothrombinase complex in a thrombophilic family

“…All subjects showed PT levels within the normal range, and only a weak correlation was observed between carriership of the PT 20210G/A mutation and high PT levels. F1 ϩ 2 levels (Figure 1) were also determined as an integrated measure of prothrombinase activity, 41 and the highest values were observed in carriers of double defects and particularly in those who had experienced venous thromboembolism.…”

A genetic basis for the interrelation of coagulation factors

“…Assays were performed in the investigators’ laboratories. Antigen plasma concentrations of FV [in‐house assay; interassay coefficient of variation (CV) 7%] [9], FVII (CV 7%), FVIII (CV 8%), FIX (CV 10%), FX (CV 7%), VWF [10] (CV 3%) and total TFPI (CV 6%) were measured by enzyme‐linked immunosorbent assay, and antigen levels of prothrombin [11] (CV 6%), antithrombin [12,13] (CV 5%), and free protein S [14] (CV 10%) were determined by radioimmunoassay. The Clauss method was used for determining the plasma concentration of fibrinogen [15,16] (CV 2%), using the ST4 instrument (Diagnostica Stago, Parsipanny, NJ, USA).…”