Thirty-seven trial arms (n=5,822) from 20 RCTs were included in the review.
The rate of venous thromboembolism recurrence while taking oral anticoagulants was 0.49% per month; 0.38% of patients had major haemorrhages. Venous thromboembolism recurrences were 2.62 times as frequent in the two months following discontinuation of oral anticoagulation (1.57% per month) as subsequently (0.56% per month, OR 2.62, 95% CI 2.19 to 3.14), which meant 2.02% of patients had rebound hypercoagulability-related venous thromboembolism recurrence.
Analysis of the trials that assessed longer and shorter duration of anticoagulation therapy found lower rates of venous thromboembolism recurrence with longer duration of therapy; removal of a large trial labelled as an outlier from the analysis meant this difference was no longer apparent and there were no differences in total adverse events between the groups (11 RCTs).