Evidence that factor VII levels correlate strongly with fibrinopeptide A release: evaluation by an ex vivo method

The generation of thrombin was estimated by an assay for fibrinopeptide A which was developed and employed to evaluate the relationship between factor VII and thrombin release. The amount of fibrinopeptide A released correlated strongly, when assayed in the early stages of the reaction, with factor VII coagulant activity levels in the range 50-2,000 units/dl. The method was then applied to study the relationship between factor VII and fibrinopeptide A in plasma from blood donors, women on the pill and patients on oral anticoagulants (with a range of factor VII coagulant activity from 8.5 to 600 units/dl). The overall evaluation of the relationship between factor VII and fibrinopeptide A showed a strong correlation which was higher for factor VII coagulant activity (r = 0.90) than for factor VII antigen levels (r = 0.817). The regression analysis which best fitted the data was the multiplicative one, indicating that thrombin formation increases faster when factor VII coagulant activity is in the upper part of the normal range or higher. In patients on oral anticoagulants, the correlation between factor VII and fibrinopeptide A was very poor. Our data fit well with the findings of the epidemiological studies in which high levels of factor VII coagulant activity were shown to be associated with an increased incidence of fatal coronary artery disease.