Long-term outcome of venous thrombosis

Venous thrombosis occurs in, on average, one in every thousand individuals per year. Risk factors include older age, concurrent malignant/inflammatory/other diseases, hospital admission/surgery/immobilization, pregnancy and use of external estrogens. Thrombosis is treated with anticoagulants drugs. Overall, this treatment is very effective but associated with an increased risk of bleeding. Current follow-up of cohorts with thrombosis focusses mainly on the risk of recurrent thrombosis, as this informs the recommended duration of therapy with anticoagulation (reviewed in Khan F et al, BMJ 2019;24:I4363). 

In subgroups, for instance in those with malignancy-associated thrombosis, data are available on the influence of thrombosis on survival (for instance, Sorensen HT, N Engl J Med 2000;343:1846). For the general population with thrombosis, these data are scarce. Although in daily clinical practice, we see that patients with thrombosis often to not return to their baseline functional level (Mäkelburg ABU, thesis RUG 2014), data on social participation are not available.

Another issue is the risk of thrombosis in family members. It is well recognized that individuals have different baseline risk of thrombosis, and that these differences have a genetic background. We and others have published on the risk of thrombosis associated with well recognized genetic abnormalities and variations. In these studies, we found that individuals without the familial mutation/polymorphism still had a thrombosis risk that exceeded that of the general population (Middeldorp et al, Ann Intern Med 1998;128:15-20; Mahmoodi BK et al, J Thromb Haemost 2010;8:1193-200). This is consistent with the observation that a positive family history for thrombosis in itself is a risk factor for thrombosis. Data are lacking on how large this risk is and whether it is depended on characteristics of the index thrombosis/patient.

The Lifelines cohort could provide a really long term follow up of thrombosis outcomes, provided that we can validate the self-reported baseline data. For thrombosis diagnosed and treated before 2014, these are expected to be all registered with Certe Thrombosis Service (as until 2014, only oral anticoagulation managed by Thrombosis Services was available). Our group has done a similar validation project in the PREVEND cohort (Mahmoodi BK et al, JAMA 2009;301:1790-7; Van Schouwenburg IM, Br J Haematol 2012;156:667-71). For thrombosis diagnosed and treated in or after 2014, patients should either be registered with Certe or should be prescribed anticoagulation (of the DOAC type) through their community pharmacy.