Het VISTA onderzoek:
Het VTE-predictiemodel als leidraad voor de duur van antistollingstherapie binnen de huidige richtlijnen voor patiënten met een veneuze-tromboembolie.

Rationale:

Treatment of venous thrombo-embolism (VTE)- both deep venous thrombosis (DVT) and pulmonary embolism (PE)- with vitamin K antagonists (VKA) is highly effective in reducing morbidity and mortality. However, after standard VKA discontinuation after 6 months there is considerable risk of VTE recurrence, about 9 % after one year and 30% after 5 years. Long term treatment with VKA reduces risk of VTE recurrence to 1% a year, but at a cost of 2% increase in risk of major bleedings. There is limited evidence (and ongoing discussion) about the optimal treatment duration of VKA, given the challenge to obtain reduction in recurrent VTE thereby sustaining acceptable (low) risk of bleeding. Recently, a prediction model has been developed that accurately predicts the risk of VTE recurrence in patients with a first episode of unprovoked VTE. This strategy could give caregivers a more objective tool to tailor optimal duration and increase cost-effectiveness of VKA therapy in patients with VTE.



Objective:

To quantify the cost-effectiveness and safety of formal applying the guideline evaluating the risk-benefit ratio and the duration of anti-coagulant therapy by a previously developed VTE recurrence prediction model in patients with a first episode of unprovoked VTE as compared to care-as-usual.



Study design:

A single-centre, pragmatic randomized trial in patients with a documented first episode of unprovoked DVT or PE with a follow-up of 24 months.



Study population:

All adult patients, referred to their local Thrombosis Service Centre care for routine anti-coagulant treatment because of a confirmed first VTE.



Intervention:

Prediction model guided treatment (in high-risk patients, the initial, standard 6 months VKA treatment is continued for the entire follow-up period of 24 months whereas in low-risk patients long-term treatment is stopped after the standard initial period of 6 months) compared to care-as-usual.



Main study parameters/endpoints:

Primary outcome: Occurrence of major bleedings within 24 months of follow-up.

Secondary outcomes:

1. Occurrence of major bleedings;

2. Quality of life;

3. Cost-effectiveness.



Nature and extent of the burden and risks associated with participation, benefit and group relatedness:

At baseline, several patient characteristics will be asked to all patients. Patients randomized to the index group may undergo a maximum of 3 venipuncture for D-dimer testing during the treatment phase of the study. For comparison reasons, patients randomized to the control group also undergo a venipuncture for D-dimer testing at the end of treatment with VKA. Furthermore, all patients will visit their local Thrombosis Service at 12 and 24 months during the follow-up phase in which Quality of Life’ questionnaires will be asked and data for cost-effectiveness analyses.

Formalization of the current guidelines on VTE treatment duration with VKA, by means of using a VTE recurrence prediction model in patients with venous thrombo-embolism, will optimize its cost-effectiveness compared to care-as-usual. Only patients with high-risk of VTE recurrence will receive indefinite treatment in absence of a high bleeding risk. In low-risk patients, the use of possible bleeding risk-enhancing anticoagulants can be minimized safely and confined to the fixed duration as stated in the current guidelines.

Follow up:
1. 3 months;

2. 12 months;

3. 24 months.

Formalization of guidelines on duration of treatment, based on outcome of VTE recurrence prediction model compared to care-as-usual (that is: duration by physician’s decision).