Activation markers of coagulation and fibrinolysis in twins:: heritability of the prethrombotic state

Background Activation markers of coagulation and fibrinolysis are increased in individuals at risk of coronary-artery disease and other thrombotic disorders-a condition defined as the prethrombotic state. We aimed to find out the extent to which the prethrombotic state is determined by genetic factors. Methods We analysed concentrations of prothrombin, prothrombin fragment 1+2, thrombin-antithrombin complex, crosslinked fibrin degradation product D-dimer, and thrombin-activatable fibrinolysis inhibitor by ELISA in 118 monozygotic and 112 dizygotic unselected female twins aged 21-73 years from the St Thomas' UK Adult Twin Registry. We used quantitative genetic-model fitting to estimate heritability. Findings We found significant heritabilities in concentrations of the activation markers in plasma. Genetic factors contributed 45, 40, and 65% of the variation in concentrations of fragment 1+2, thrombin-antithrombin complex, and D-dimer, respectively. Age was important only in fragment 1+2 concentrations, in which it accounted for 12% of the variation. The remaining variation could be attributed to unique environmental factors. Variation in concentrations of precursor prothrombin in plasma was determined by 57% heritability, and that of zymogen thrombin-activatable fibrinolysis inhibitor showed a very strong genetic component (82%). Interpretation The activation mechanisms of the coagulation and fibrinolytic systems, and therefore the prethrombotic state, are controlled to a substantial degree by genetic factors. Genes influencing activation of haemostasis are likely to be an important component of the overall thrombotic tendency in the general population.