Condition category
Circulatory System
Date applied
Date assigned
Last edited
Prospectively registered
Overall trial status
Recruitment status
No longer recruiting

Plain English Summary

Not provided at time of registration

Trial website

Contact information



Primary contact

Prof Kevin Mackway-Jones


Contact details

Emergency Department
Manchester Royal Infirmary
Oxford Road
M13 9WL
United Kingdom
+44 (0)1612 766781

Additional identifiers

EudraCT number number

Protocol/serial number


Study information

Scientific title

The Anticoagulation of Calf Thrombosis (ACT) Study: a randomised controlled trial comparing standardised anticoagulation versus conservative therapy in the treatment of below knee deep vein thrombosis



Study hypothesis

The treatment of a blood clot in the leg below the level of the knee is a long debated topic. There is ongoing discussion about whether to treat this condition actively with drugs to thin the blood (anticoagulants) or to simply 'watch and wait'. Both approaches are utilised at different hospitals in the North West.

Some hospitals 'watch and wait' only. They scan the leg 1 week after presentation, treating only if the clot gets bigger. Several research studies suggest this is as safe an approach as treating the clot. It also avoids exposing patients to the inherent risks of blood thinning drugs.

Other hospitals worry about the chance of the clot moving up the leg and rarely into the lungs. They practice treating all patients with anticoagulants to reduce these risks as much as possible. This also means that patients do not have to come back in a weeks time for another scan. Although some risk may be reduced by this approach, there is a potential for anticoagulant drugs to cause harm.

This research is trying to find out which approach is safest for patients. To find this out, we propose to randomly allocate patients with below knee blood clots to receive conservative treatment, (stocking supports and simple painkillers), or conservative treatment and
anticoagulation. All patients will receive serial leg scans and be followed closely. Short-term assessment and long term follow up will occur.

If the trial shows a benefit from treating below knee clots, this will have a major impact on those hospitals which only scan above the knee, as many currently do. If the trial shows no benefit to treating the clots, many patients will be able to avoid the dangers of anticoagulation and further risk.

This feasibility trial will look to establish the percentage of recruitable patients from available cohort and feasibility of maintaining treatment allocation for three months.

Ethics approval

The North West 7 Research Ethics Committee (REC) - GM Central approved on the 15th of November 2010 subject to a complete response to request for further information (ref: 10/H1008/97)

Study design

Prospective open label randomised controlled trial

Primary study design


Secondary study design

Randomised controlled trial

Trial setting


Trial type


Patient information sheet

Not available in web format, please use contact details below to request a patient information sheet


Calf thrombosis/below knee DVT


Patients will be randomised to one of the following treatment groups
1. Group A: conservative treatment (TED stockings and simple analgaesia) and full-dose anticoagulation, initiated with Low Molecular Weight Heparin (LMWH) (dalteparin, dosage based on weight) then converted to oral anticoagulation with warfarin for a duration of 3 months total. Warfarin dosing to be based on International Normalized Ratio (INR) blood clotting measurements aiming for a target range of 2-3.
2. Group B: conservative treatment only

All patients will have vascular ultrasound scans at 7 days and 21 days to look for propagation or clot development, along with clinical review. All patients will be clinically followed for the three month duration of treatment. All patients will also be reviewed at two years regarding assessment for post-thrombotic leg syndrome.

Intervention type



Phase IV

Drug names

Primary outcome measure

Combined incidence of thrombus propagation above knee or development of pulmonary embolism during the 3 months randomisation period

Secondary outcome measures

1. Incidence of major and minor bleeding episodes
2. Incidence of post thrombotic leg syndrome at 2 years using validated screening tool
3. Incidence of DVT recurrence at 2 years

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

1. All ambulatory outpatients presenting to Manchester Royal Infirmary Emergency department diagnosed with below knee calf vein thrombosis by vascular ultrasound scan (USS)
2. Able to give informed consent
3. Aged 16-90

Participant type


Age group




Target number of participants

100 for primary feasibility

Participant exclusion criteria

1. Hospitalised patients
2. Patients on long-term anticoagulation
3. Associated proximal DVT or confirmed PE
4. Contraindication to anticoagulation (active bleeding, recent haemorrhagic CVA or upper GI bleed)
5. Other indication for immediate warfarinisation as per BSH guidelines: Prior confirmed and treated above knee DVT/PE, antiphospholipid syndrome, symptomatic inherited thrombophilia
6. Pregnancy
7. Chronic non propagating thrombus seen on prior USS
8. Previous enrolment to the ACT study and achievement of the primary outcome

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Emergency Department
M13 9WL
United Kingdom

Sponsor information


Central Manchester NHS Foundation Trust (UK)

Sponsor details

c/o Lynne Webster
Research and Development
1st Floor Postgraduate Centre
Manchester Royal Infirmary
Oxford Road
M13 9WL
United Kingdom
+44 (0)1612 763565

Sponsor type

Hospital/treatment centre



Funder type


Funder name

College of Emergency Medicine (UK)

Alternative name(s)


Funding Body Type

private sector organisation

Funding Body Subtype



United Kingdom

Results and Publications

Publication and dissemination plan

Not provided at time of registration

Intention to publish date

Participant level data

Not provided at time of registration

Basic results (scientific)

Publication list

2012 protocol in:
2014 results in:

Publication citations

  1. Protocol

    Horner D, Hogg K, Body R, Nash MJ, Mackway-Jones K, The Anticoagulation of Calf Thrombosis (ACT) project: study protocol for a randomized controlled trial., Trials, 2012, 13, 31, doi: 10.1186/1745-6215-13-31.

  2. Results

    Horner D, Hogg K, Body R, Nash MJ, Baglin T, Mackway-Jones K, The Anticoagulation of Calf Thrombosis (ACT) project: results from the randomized controlled external pilot trial., Chest, 2014, doi: 10.1378/chest.14-0235.

Additional files

Editorial Notes