1. Clinical Knowledge Summaries CKS Deep venous thrombosis (DVT)
Diagnosis and management in primary care.
Educational slides based on the CKS topic DVT (April 2013) and NICE guidance (2012a): Venous thromboembolic disease: the management of venous thromboembolic diseases and the role of thrombophilia testing.

2. Key learning points and objectives
To be able to:
Assess the likelihood of a DVT being present, using the two-level DVT Wells score.
Recognise people who are considered to be at high risk of DVT and need same day assessment.
Describe when it is appropriate to give a parenteral anticoagulant and which one should be offered.
Outline what management and follow up is required after discharge from hospital.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

3. DVT – background information
DVT is the formation of a blood clot in a deep vein.
Usually in the legs; partially or completely obstructs blood flow.
Annual incidence is about 1 in 1000 people.
The most serious complication is pulmonary embolism.
Only about a third of people with a clinical suspicion of DVT have the condition.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

4. Risk factors for DVT Risk factors include:
Previous venous thromboembolism.
Cancer (known or undiagnosed).
Increasing age.
Being overweight or obese.
Male sex.
Heart failure.
Acquired or familial thrombophilia.
Chronic low-grade injury to the vascular wall (for example vasculitis, hypoxia from venous stasis, or chemotherapy).
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

5. Temporary risk factors
Risk factors that temporarily raise the likelihood of DVT:
Immobility, significant trauma, or direct trauma to a vein.
Hormone treatment (for example oestrogen-containing contraception or hormone replacement therapy).
Pregnancy and the postpartum period.
Dehydration.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

6. What else might it be? Physical trauma: Calf muscle tear or strain.
Haematoma (collection of blood) in the muscle.
Sprain or rupture of the Achilles tendon.
Fracture.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

7. What else might it be? Cardiovascular disorders:
Superficial thrombophlebitis.
Post-thrombotic syndrome.
Venous obstruction or insufficiency, or external compression of major veins (for example by a fetus during pregnancy, or cancer).
Arteriovenous fistula and congenital vascular abnormalities.
Acute limb ischaemia.
Vasculitis.
Heart failure.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

8. What else might it be? Other conditions including:
Ruptured Baker's cyst.
Cellulitis (commonly mistaken as DVT).
Dependent (stasis) oedema.
Lymphatic obstruction.
Septic arthritis.
Cirrhosis.
Nephrotic syndrome.
Compartment syndrome.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

9. When to suspect a DVT Suspect a DVT if the person has:
Signs or symptoms of a DVT:
Pain and swelling in one leg, although both legs may be affected.
Tenderness, changes to skin colour and temperature, and vein distension.
A risk factor for DVT (e.g. previous VTE and immobility).
To exclude an alternative cause:
Carry out a physical examination.
Review the person's general medical history.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

10. Managing a suspected DVT
Refer immediately if pregnant or given birth within the past 6 weeks.
Requires same-day assessment and management as it is not possible to accurately assess the risk of DVT in primary care.
For everyone else, use the two-level DVT Wells score to assess likelihood of DVT and inform further management.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

11. Two-level DVT Wells score
Validated, simple scoring system that takes into account previous DVT.
DVT is likely if the score is two points or more.
DVT is unlikely if the score is one point or less.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

12. Using the two-level DVT Wells score
Score one point for each of the following:
Active cancer (treatment ongoing, within the last 6 months, or palliative).
Paralysis, paresis, or recent plaster immobilization of the legs.
Recently bedridden for 3 days or more, or major surgery within the last 12 weeks requiring general or local anaesthetics.
Localized tenderness along the distribution of the deep venous system (such as the back of the calf).
Entire leg is swollen.
Calf swelling by more than 3 cm compared with the asymptomatic leg (measured 10 cm below the tibial tuberosity).
Pitting oedema (greater than on the asymptomatic leg).
Collateral superficial veins (non-varicose).
Previously documented DVT.
Subtract two points if an alternative cause is considered more likely than DVT.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

13. Other methods of assessment
Do not use:
Individual symptoms and signs on their own.
On their own they are poor predictors of the presence or absence of DVT. 
A positive Homans' sign (pain in the calf or popliteal region on passive, abrupt, forceful dorsiflexion of the ankle with the knee in a flexed position):
Is insensitive and nonspecific.
Can be painful, and there is a theoretical possibility of dislodging a thrombus.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

14. If DVT likely (>2 points)
Refer for a proximal leg vein ultrasound scan to be carried out within 4 hours.
If a proximal leg vein ultrasound scan cannot be carried out within 4 hours of being requested:
Take a blood sample for D-dimer testing.
Give an interim 24-hour dose of a parenteral anticoagulant (weight required to calculate the dose).
Ensure a proximal leg vein ultrasound scan is carried out within 24 hours of being requested.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

15. Which parenteral anticoagulant?
Offer a choice of low molecular weight heparin (LMWH) or fondaparinux.
Licensed LMWHs for DVT treatment include dalteparin, enoxaparin, and tinzaparin.
Fondaparinux is a synthetic pentasaccharide that inhibits activated factor X.
Choice of parenteral anticoagulant depends on:
Comorbidities, contraindications, and cost.
Local policy may also influence choice.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

16. If DVT unlikely (< 1point)
Offer D-dimer testing.
If negative D-dimer test - consider an alternative diagnosis to explain symptoms.
If positive D-dimer test - refer for a proximal leg vein ultrasound scan to be carried out within 4 hours.
If a proximal leg vein ultrasound scan cannot be carried out within 4 hours of being requested:
Give an interim 24-hour dose of a parenteral anticoagulant (weight required to calculate the dose).
Ensure a proximal leg vein ultrasound scan is carried out within 24 hours of being requested.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

17. Treatment in secondary care
Once a DVT has been confirmed in secondary care, most people will be initiated on long term treatment (3 months or longer) with either:
An oral anticoagulant (warfarin or rivaroxaban), or
A LMWH.
LMWH are usually indicated if oral anticoagulants are:
Contraindicated, for example pregnancy, or
Less preferred, for example cancer.
Presenter notes
Bridging therapy with heparin or a low molecular weight heparin is given concomitantly if warfarin therapy is initiated. This is because it can take 48 to 72 hours (or longer) for the anticoagulant effect of warfarin to fully develop (CKS topic Anticoagulation – oral; May 2013).
Rivaroxaban has a faster onset of action of 2-4 hours (Rivaroxaban monograph, Micromedex; last updated March 2014).
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

18. Follow up for DVT At follow up ensure:
That people with an unprovoked DVT are:
Investigated for the possibility of an undiagnosed cancer, and
Have been offered thrombophilia testing, as appropriate.
Adequate regular monitoring for warfarin or rivaroxaban.
Monitoring requirements for warfarin and rivaroxaban differ.
That below-knee compression stockings have been prescribed.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

19. Monitoring warfarin
For people taking warfarin monitor the international normalized ratio (INR) and adjust the dose as required.
The target INR for people with a DVT is between 2 and 3 (ideally 2.5).
Usually monitor INR:
Initially - daily, or every other day, until within therapeutic range, then
Twice weekly for 1–2 weeks, then
Weekly until at least two INR measurements are within range, thereafter
Depends on the stability of the INR but usually longer intervals (e.g. up to every 12 weeks).
Based on the CKS topic Anticoagulation – 0ral (May 2013)

20. Monitoring rivaroxaban
No need to monitor the INR, however
Regular follow up and monitoring is still required.
Follow up every 3 months to assess for:
Concordance and adverse effects (e.g. bleeding).
Repeat renal and liver function tests as well as the full blood count at least once a year.
Repeat renal function tests:
Every six months if the person has a creatinine clearance (CrCl) of 30–60 mL/min.
Every three months if the person has a CrCl of 15–30  mL/min.
If renal function has declined, review treatment.
Rivaroxaban may need to be stopped or the dose lowered.
Based on the CKS topic Anticoagulation – 0ral (May 2013)

21. Compression stockings
Before prescribing:
Exclude arterial insufficiency.
Check the condition of the skin.
Fragile skin may be damaged when putting on or taking off stockings.
Consider if the person in likely to be able to manage the stockings.
Arthritis - may be difficult to get stockings on and off.
May need application aid/help from community nurse.
Based on the CKS topic Compression stockings (September 2012).

22. Compression stockings
Class 3 stockings are preferred but may be poorly tolerated.
Class 2 can be used as an alternative.
Usually worn for 2 years (unless there are contraindications).
Prescribe a spare pair (one to wear and one in the wash).
Renew every 3–6 months.
Re-measure leg each time to ensure correct fit.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

23. Advice to patients Walk regularly after discharge from hospital.
Elevate the affected leg when sitting.
Refrain from extended travel, or travel by aeroplane, for at least 2 weeks after starting anticoagulant treatment.
Based on the CKS topic DVT (April 2013) and NICE guidance (2012a); Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing.

24. Summary
Only a third of people with a clinical suspicion of DVT have the condition.
If DVT suspected and the person is pregnant or has given birth within the past 6 weeks – refer immediately.
For everyone else use the two-level DVT Wells score to assess likelihood of DVT.
DVT is likely if the score is two points or more.
DVT is unlikely if the score is one point or less.
If DVT likely, refer for a proximal leg vein ultrasound scan (carried out within 4 hours).
Give a parenteral anticoagulant and do a d-dimer test if ultrasound cannot be carried out with in 4 hours.
If DVT unlikely, offer D-dimer test, if positive - refer for proximal leg vein ultrasound scan (carried out within 4 hours).
Give a parenteral anticoagulant if ultrasound cannot be carried out with in 4 hours.