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Scenario: Management of deep vein thrombosis



Management of suspected DVT for patients aged from 16 years onwards


How should I manage suspected deep vein thrombosis?


    Refer immediately for same-day assessment and management, if deep vein thrombosis (DVT) is suspected in a woman who is pregnant or has given birth within the past 6 weeks.


For all other people with suspected DVT, use the two-level DVT Wells score to assess the probability of a DVT.

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.

•The risk of DVT is likely if the score is two points or more, and unlikely if the score is one point or less.


For people who are likely to have DVT (based on the results of the two-level DVT Wells score):

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 (note that the weight of the person will be required to   calculate the dose of parenteral anticoagulant). For more information on prescribing parenteral anticoagulants,   see the section on Parenteral anticoagulants in prescribing information.

•Arrange for a proximal leg vein ultrasound scan (to be carried out within 24 hours of being requested).

 

For people who are unlikely to have DVT (based on the results of the two-level DVT Wells score), offer D-dimer testing:


If the D-dimer test is positive, 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 (note that the weight of the person will be required to calculate the dose of parenteral anticoagulant). For more information on prescribing parenteral anticoagulants, see the section on Parenteral anticoagulants in prescribing information.


Arrange for a proximal leg vein ultrasound scan (to be carried out within 24 hours of being requested).

If the D-dimer test is negative, consider an alternative diagnosis to explain symptoms.


Basis for recommendation


These recommendations are based mainly on a National Clinical Guideline Centre guideline (commissioned by the National institute for health and Care Excellence [NICE]): Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing[National Clinical Guideline Centre, 2012a; NICE, 2012a], a Scottish Intercollegiate Guidelines Network (SIGN) guideline:


Prevention and management of venous thromboembolism[SIGN, 2010], and an evidence-based review article produced by the British Committee for Standards in Haematology (BCSH) [Keeling et al, 2004].


Referral of pregnant and postpartum women


Referral recommendations are based on expert opinion of the Royal College of Obstetricians and Gynaecologists [RCOG, 2010]. Referral for objective testing for deep vein thrombosis (DVT) is required because it is not possible to accurately assess the risk of DVT in primary care based on the usual methods of assessment because:

•The Wells Clinical Prediction Rule can not be used to assess DVT risk in pregnant women.

•The usefulness of D-dimer testing is limited by a high rate of false positive results in pregnancy.


Management of suspected DVT based on results of the two-level Wells score


These recommendations are based on a guideline commissioned by NICE [NICE, 2012a].

The recommendations are also consistent with recommendations in an evidence-based American guideline which states that [Kearon et al, 2012]:

 

In people with a high clinical suspicion of acute VTE, treatment with parenteral anticoagulants should be commenced while awaiting the results of diagnostic tests.


In people with an intermediate clinical suspicion of acute VTE, treatment with parenteral anticoagulants should be commenced if the results of diagnostic tests are expected to be delayed for more than 4 hours.


However, in people with a low clinical suspicion of acute VTE, not treating with parenteral anticoagulants is suggested while awaiting the results of diagnostic tests provided test results are expected within 24 hours.


The Wells score


The Wells Clinical Prediction Rule (referred to as the Wells score by NICE) is a clinical tool which was originally developed in 1997 following a cohort study (n = 593) which identified the most important risk factors in people with DVT [Wells et al, 1997].


Although there are several versions of the Wells score available, NICE recommends the two-level DVT Wells score which was described in 2003 following a randomized controlled trial (RCT, n = 566) that validated the test [Wells et al, 2003]. According to NICE, compared with other versions, the two-level DVT Wells score is more relevant, up to date, and consistent with their latest understanding of VTE risks [NICE, 2012a].


The two-level DVT Wells score [NICE, 2012a]:


Takes into account previous DVT, which is a major risk factor for subsequent DVT. People who had had a previous DVT were excluded from the original cohort study.


Has a simplified scoring system, allocating people to one of two groups, 'likely' or 'unlikely'. The original rules allocated people to three groups, with an additional group described as being at moderate or intermediate risk (in practice, management of this group in primary care does not differ from those who are considered to be at high risk). NICE states that 'when a dichotomous scoring system is used (likely/unlikely), these are much easier to be implemented correctly because there is less chance of confusion about what to do with the moderate group in the old system'.


Has a longer duration of risk after surgery (12 weeks compared with 4 weeks in the original version).


D-dimer test


The formation of thrombus is normally followed by an immediate fibrinolytic response, resulting in generation of plasmin which causes the release of fibrin degradation products (predominantly containing D-dimer) into the circulation. A negative D-dimer assay therefore implies that thrombosis is not occurring and thus has a role in excluding a diagnosis of DVT (along with clinical scores and imaging). Although a positive D-dimer result can indicate thrombosis, other possible causes of a raised D-dimer include liver disease, inflammation, malignancy, pregnancy, trauma, and recent surgery [National Guideline Clearinghouse, 2012].


D-dimer tests have relatively high sensitivity but low specificity (false positive results are common). Therefore, whilst a negative D-dimer may be useful in excluding DVT, a positive D-dimer is of no diagnostic value, but merely mandates further testing.


A negative D-dimer test is good enough to exclude the diagnosis of DVT in people with an unlikely pre-test clinical probability, but it is not good enough to exclude the diagnosis of DVT in those with a likely pre-test probability.



Follow up for DVT


How should I follow up a person with confirmed deep vein thrombosis?


Provided there are no contraindications (such as pregnancy or cancer), people who have been diagnosed with deep vein thrombosis (DVT) will require maintenance treatment with an oral anticoagulant drug (warfarin or rivaroxaban) following acute treatment.


Ensure adequate monitoring — see the CKS topic on Anticoagulation - oral.


Specialists will make clinical decisions such as the choice of anticoagulant and the duration of treatment.


Treatment is usually continued for at least 3 months, but duration may be longer depending on whether the DVT was unprovoked (no obvious, transient risk factor identified) or provoked (caused by an identifiable, transient, major risk factor).


For warfarin, the usual strategy is to aim for an international normalized ratio (INR) target of 2.5, keeping within the range of 2.0–3.0. Rivaroxaban does not require any coagulation monitoring or regular dose adjustments.


Ensure that people with unprovoked DVT are investigated for the possibility of an undiagnosed cancer if they are not already known to have cancer (see Investigations for cancer for more information).


Ensure that people with unprovoked DVT have been offered thrombophilia testing, as appropriate (see Thrombophilia testing for more information).


Most people who are diagnosed with DVT require below-knee compression stockings.


Class 3 (25 mmHg to 35 mmHg) are recommended. However, class 2 stockings (18 mmHg to 24 mmHg) may be used if class 3 stockings are poorly tolerated.


Compression stockings are recommended for a duration of 2 years (unless there are contraindications). However, people with established post-phlebitic symptoms will probably benefit from ongoing use of compression stockings (that is, for more than 2 years).


A spare pair of compression stockings should be prescribed at any one time so that the person has a pair to wear when the other one is being washed.


The prescription for compression stockings should be renewed every 3–6 months or according to the manufacturer's instructions. Ideally the leg should be re-measured each time to ensure correct fit.


For more information on using compression stockings, see the CKS topic on Compression stockings.


Advise the person:


To engage in regular walking exercise after they are discharged from hospital (unless a specialist advises against this).

      

That the affected leg should be elevated when sitting.


That extended travel, or travel by aeroplane, should be delayed until at least 2 weeks after starting anticoagulant treatment. Travel within 2 weeks of a DVT is not recommended without seeking advice from a specialist. For more information, see the section on Recent DVT in the CKS topic on DVT prevention for travellers.

United Kingdom Scenario as offered by NICE, National Institute for Health and Care Excellence