According to this study:

* Patients at low risk for recurring venous thromboembolism can be identified according to thrombin generation measurement.

* Such patients may not need indefinite anticoagulation therapy.

According to a recently published Austrian study, in patients who had suffered initial spontaneous venous thromboembolism (VTE) there was a 60% lower risk of recurrent VTE if they had a peak thrombin generation value of less than 400 nm. The researchers sought to determine the relationship between recurrent clots and thrombin generation to help in the identification of patients who would benefit most from indefinite anticoagulation therapy.

The prospective, cohort study conducted over a 13-year period consisted of 914 subjects, all of whom had had spontaneous initial VTE for which they had received at least three months of treatment with a vitamin K antagonist (excluding patients who had cancer, were pregnant, had had recent surgery or trauma, or had undergone anticoagulation therapy for reasons other than VTE). The subjects were followed for an average of 47 months from the time of discontinuation of vitamin K antagonist therapy, and blood samples were obtained for an assay of thrombin generation levels after a median period of 13 months following the discontinuation of anticoagulant therapy. The primary end point of the study was the recurrence of symptomatic VTE (either a deep vein thrombosis or pulmonary embolism).

Of the 914 patients, 11% (n = 100) had recurrent VTEs-58 from deep vein thrombosis and 42 from pulmonary embolism. Overall, patients who did not suffer subsequent VTEs had a lower peak thrombin generation value than those who did (349.2 nm and 419.5 nm, respectively). One-third had peak thrombin values of 400 nm or greater, and the rest had values either between 300 nm and 400 nm or less than 300 nm, in comparable numbers. A univariate analysis revealed a relative risk of recurrent VTE of 0.42 among the patients with values in the 300 nm to 400 nm range and a relative risk of 0.37 among those with values of less than 300 nm. A multivariate analysis that adjusted for confounding factors such as age, sex, body mass index, and site of the initial VTE did not change the relative risks significantly. At four years, patients with peak thrombin values of less than 400 nm demonstrated a 6.5% probability of recurrent VTE, while those with values of 400 nm or greater demonstrated a 20% probability of recurrence.

The use of a thrombin generation assay, a simple and inexpensive laboratory test, showed that a majority of subjects had little risk for recurrent VTE. This suggests that it is possible to reduce the use of anticoagulation therapy in such patients without increasing the risk of recurring clot formation.