Thrombin generation profile in non-thrombotic factor V Leiden carriers

Factor V Leiden (FVL) mutation is the most common genetic risk factor for venous thromboembolism. In families with a history of thrombosis, FVL can be present in 18%. Thrombin generation test is commonly used as an evaluation tool of thrombotic risk. The objective of this study was to evaluate the thrombogenic potential of FVL in asymptomatic carriers and in patients with personal or familial history of thrombosis. This was a retrospective single center study including 160 patients. Among them, 43 had personal history of thrombosis and 117 had familial history of thrombosis. Thrombin generation (TG) was realized in frozen platelet poor plasma with 1 pM of tissue factor and 4 mu M of phospholipid. FVL mutation was associated with a global increase of TG. No difference was observed between patients with provoked thrombosis and patients with first-degree familial history of thrombosis (endogenous thrombin potential (ETP): 1501.0 +/- 316.4nMmin and thrombin peak: 253.4 +/- 71.5nM vs. 1520.4 +/- 283.8nMmin and 268.6 +/- 68.0nM). An increase of TG was observed in patients with unprovoked thrombosis (n=23) and in patients with provoked thrombosis (n=20) (ETP: 1819.5 +/- 319.8nMmin and peak: 332.3 +/- 55.8nM). In the unprovoked thrombosis group, patients with a pulmonary embolism had a higher ETP than patients with deep vein thrombosis (DVT) (2036 +/- 343nMmin vs. 1707 +/- 261nMmin). With a predictive score formula (s=0.1315 x Age+0.0105 x ETP) with a threshold of 22.1 as risk to develop an unprovoked thrombosis among patients with second-degree familial history. The results of our analysis suggest that measurement of thrombin generation in patients with FVL mutation may identify subjects with an increased risk of unprovoked thrombosis. Further studies are needed to examine the usefulness of predicting thrombotic presentation in asymptomatic carriers.