MEGA follow-up study


Project managers

Prof. dr S.C. Cannegieter

Dr W.M. Lijfering

Dr A. van Hylckama Vlieg 

Prof. dr F.R. Rosendaal

After a first venous thrombotic event the risk of recurrence is high. Estimates of the five-year cumulative incidence of recurrent venous thrombosis range from 12 to 25% in literature.

Especially after a recurrent event, the risk of chronic complications, such as post-thrombotic syndrome, is high. Therefore, secondary prevention of venous thrombosis is very important. Secondary prevention can be achieved either by prolonging anticoagulant treatment in patients with high risk of recurrence or by elimination of risk factors. Remarkably, the risk profile for recurrent venous thrombosis is different from that for a first event and not that many risk factors for recurrent venous thrombosis are currently known.

Over 4700 patients with a first venous thrombosis, who participated as cases in the MEGA case-control study, were followed over time for recurrent venous thrombosis. Mean follow-up was almost five years. About 700 cases of recurrent venous thrombosis have been verified by information from patients, anticoagulation clinics and treating physicians. Baseline (time of first venous thrombosis) data are available, including detailed risk factor status (surgery, immobilisation, hormone use, co-morbidity, BMI, etc) and laboratory measurements. Additionally, we received a second detailed questionnaire on risk situations (e.g. arterial risk factors, inflammation, other co-morbidity, medication) during follow-up from more than 2800 patients.  

The MEGA follow-up study is one of the largest follow-up studies on recurrent venous thrombosis. The aim of the MEGA follow-up study is to reliably estimate the incidence of recurrent venous thrombosis (deep vein thrombosis and/or pulmonary embolism) and to identify risk factors for recurrence. Both genetic and environmental risk factors are currently under study, as well as the combined effect of thrombotic risk factors. Furthermore, these results have been used to identify patients with high risk of recurrence, by means of the L-TRRiP score (Leiden-Thrombosis Recurrence Risk Prediction), who might be targeted for prolonged anticoagulant treatment.