Pot-Cast: Thrombosis Prophylaxis During Plaster Cast Lower Leg Immobilisation

Background:

Currently, guidelines and clinical practice differ considerably with respect to use of anticoagulant treatment during cast immobilization of the lower leg. Trials that have been carried out were aimed at efficacy only, had small sample sizes and therefore mainly used asymptomatic thrombosis as endpoint. From these trials an overall risk benefit-balance could not be established, hence the current controversy exists. In the proposed study we will use relevant symptomatic endpoints in a large cohort of patients. Furthermore we will follow subjects with an adverse event for a longer period, during which we will assess the long term sequelae of these events. Lastly, we will determine high risk groups that will benefit most from anticoagulant treatment.

Objective:

Comparative effectiveness research to determine cost-effectiveness of an existing healthcare policy, i.e. treatment with low molecular weight heparin (LMWH) during lower leg plaster cast immobilization following surgical or conservative treatment. In addition we will investigate personalized prophylaxis based on genetic and acquired risk factors.

Study Design:

A randomized controlled trial comparing a policy with the anticoagulant LMWH to a policy with no anticoagulant in patients with lower leg cast immobilization.

Determination of genetic and acquired risk factors will be performed at the start of the study. Based on the presence or absence of these factors we will assign a risk profile to each patient

Study Population:

The study population will consist of 1500 patients in need for a plaster cast of the lower leg, e.g. after trauma or overuse injuries of ankle and foot. These patients will be recruited from 5 hospitals in the Leiden/Den Haag region over a two-year inclusion period. All patients over 18 years will be eligible, except patients with a contra-indication or an absolute indication for LMWH use

Intervention:

LMWH (for example nadroparin 2850 IE s.c. once daily, > 100kg 5700IE sc) for the duration of the immobilization (average 6-8 weeks) vs no treatment.

Each hospital will use a LMWH according to their own preference.

Blood taken at the emergency department will be analyzed on common single nucleotide polymorphisms (SNPs) known to strongly affect thrombotic risk; on levels of coagulation factors in plasma (of which high or low levels are known to increase the risk). Patients will also be screened on acquired risk factors for thrombosis through a questionnaire.

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

We will compare two standard treatment modes that are currently both used depending on the physician's or hospital's preference. The patients in our trial will be subjected to one of these standard treatments. It is therefore not expected that participation will lead to an increased health risk. LMWHs like Nadroparin and Dalteparin are no experimental pharmaceuticals; both have been registered in the Netherlands for these indications since 1989.

Not participating in the trial may, depending on the physician, still lead to treatment with an LMWH.

All patients will need to undergo one venepuncture for blood sampling for the study. This blood sample will be taken at the first day of immobilization. No extra hospital visits are required. Patients will be contacted by an electronic questionnaire 3 weeks and 7 weeks after the start of immobilization and by telephone after three months.

One questionnaire concerning risk factors for thrombosis, bleeding and patients demographics will be filled in at the first day of cast immobilization.

Only subjects with clinically relevant adverse events (and a similar random sample of subjects without a clinically relevant adverse event) will be monitored for a two year period after the event (in total expected to be about 30 subjects). After six months, one year and two years after the event, patients will be seen for clinical examination and quality of life assessment by means of a questionnaire.