At the request of the study's funders (NIHR-HTA) the study was terminated early due to poor recruitment in the context of the COVID-19 pandemic and unprecedented pressures faced by the NHS.

Patients with a deep vein thrombosis (DVT) may develop long-term symptoms, e.g. lifelong leg pain, skin changes and occasionally ulceration, known as post-thrombotic syndrome (PTS). This affects about half of people with a history of DVT.

This randomised study aims to show whether the regular use of a compression stocking after DVT in the leg, prevents long-term pain, swelling and ulceration. Currently small trials show varied results and a large trial is required to answer the question.

Every year 1 in 1000 persons in the United Kingdom are diagnosed with a blood clot in the leg veins (deep vein thrombosis). In just under half of those with deep vein thrombosis, leg pain, swelling and skin breakdown (ulcers) can occur, a lifelong condition called post-thrombotic syndrome. This impacts upon a person's ability to work, their confidence and independence. In most patients there is no effective treatment and they lose income from unemployment. Ulcers, if they occur, require bandaging that needs to be changed twice weekly.

Treatment guidelines for deep vein thrombosis do not currently include the use of a compression stockings. They can sometimes be difficult to put on for those who cannot bend down, the stockings can slip or roll down, or become uncomfortable in hot weather. Stockings cost the National Health Service (NHS) approximately £50 every 6 months. The evidence for stockings comes from two early trials comparing patients wearing a stocking to those who did not.

There was a large benefit in both these trials for wearing a stocking, with no major side effects. In 2014, a Canadian group published a trial comparing wearing a compression stocking to wearing a non-compressive stocking. The rates of post-thrombotic syndrome were identical. The Canadian trial also suggested that only half of patients actually wear stockings, one reason the trial may have shown no difference. The Canadian trial suggested that stockings did not prevent future thrombosis or help leg pain. Whilst United Kingdom National Institute for Health and Care Excellence (NICE) recommendations are to avoid stockings after deep vein thrombosis, European recommendations are to still wear them. The contradictory results of these three trials have led us to design the CHAPS trial.

The aim of CHAPS is to confirm whether there is a real benefit of wearing stockings in addition to the standard treatment for deep vein thrombosis, which is blood thinning medication.

Adults with a first deep vein thrombosis can join the trial. They will be randomly allocated to receive either blood thinning medication, or blood thinning medication and an additional compression stocking. This is a tight, custom fitted stocking that they will be asked to wear whilst they are awake as much as possible for between 6-30 months. Patients will be aware of which group they are in, but will be asked not to wear the stocking when they come for their assessment. This keeps the researchers impartial.

Inclusion Criteria:

• Symptomatic presentation of first deep vein thrombosis, <2 weeks from diagnosis
• Imaging confirmed, lower limb deep vein thrombosis (popliteal, femoral, iliac or combination)
• Ability to give informed consent
• Age 18 or over

Exclusion Criteria:

• Life expectancy < 2 years
• Contraindication to wearing graduated compression stockings
• Previously intolerant of or already wearing graduated compression stockings for more than 1 month.
• Ankle brachial pressure index (ABPI) <0.8 or pedal pulses absent
• Bilateral deep vein thrombosis
• Previous chronic venous insufficiency (patients with existing chronic skin changes or ulceration, defined as C4,5,6 by Clinical Etiological Anatomical Pathophysiological (CEAP) classification)
• Pre-existing post thrombotic syndrome, significant leg pain (e.g. knee arthritis, spinal claudication) or oedema (e.g. lymphoedema).
• Newly diagnosed cancer, metastatic cancer, or cancer undergoing active treatment or palliation
• Contraindication to anticoagulation
• Known allergy to fabric in compression stockings

An independent researcher at each site will perform leg assessments blind to participant allocation. This researcher will not have been involved in recruitment, stocking provision, adherence monitoring or behavioural interventions. Participants will be encouraged to remove their stockings on the day prior to their clinic visit, they will be asked not to discuss the stockings with the independent assessor. Blinding will be assessed by asking the assessors whether the patient attended study visits wearing a stocking, and whether the patient made it known that they had been wearing a stocking or not.