Thrombosis experts Professor Gerry Stansby, professor of vascular surgery and honorary consultant vascular surgeon, and Dr Kathryn Musgrave, consultant haematologist and honorary senior clinical lecturer, answer key questions on how to diagnose and manage deep vein thrombosis (DVT) and thrombophlebitis
Learning objectives
This module will enhance GPs’ understanding of DVT and thrombophlebitis, including:
- How best to assess the risk of DVT in a patient presenting with calf pain.
- The prevalence of cancer in patients with seemingly unprovoked DVT.
- The value of D-dimer testing in ruling DVT in or out as part of investigations.
- Implications of a personal or family history of DVT on clinical considerations such as use of hormonal contraception or HRT.
- Management of the short- and long-term sequelae of DVT.
1. How common is DVT? Who is at particular risk?
DVT is relatively common, said to affect about 1 in every 1,000 people each year or represent a 2-5% lifetime risk. It may be even more common, as many minor cases are probably never diagnosed. Accurate figures for incidence are derived from randomised controlled trials in specific populations, mostly postsurgical, where the rate is higher. Minor calf vein DVT especially is variably scanned for and under-diagnosed, and is more common than above the knee DVT.
The main risk factors for DVT are described in the NHS Department of Health Risk Assessment tool.1 Patient related risk factors include age and obesity, cancer, pregnancy, the post-partum period, the use of oral oestrogen, first-degree relative with a history of venous thromboembolism (VTE) and periods of immobility due to severe medical illness and surgical operations. Younger patients with an unprovoked DVT may have a clotting abnormality such as thrombophilia, while older patients may have an underlying malignancy. Patients with inflammatory disease and psychiatric problems also seem to be at high risk. A history of previous DVT or pulmonary embolism (PE) increases the risk of recurrence.
2. Patients presenting with calf pain inevitably seem to get a Wells score. How useful is it, and should we be more discriminate in its use?
Unfortunately the clinical signs of DVT are very variable and sometimes minimal or overlapping with other disorders. The two-level Wells score rates DVT either clinically likely or unlikely. It is part of the diagnostic algorithm recommended by NICE for the diagnosis of DVT.2 It can be helpful, but requires clinical context.
The key final question in the two-level Wells score is to ask if an alternative diagnosis is at least as likely as a DVT. To accurately answer this question requires clinical experience and context. For example, after knee replacement surgery there will be some pain and swelling, but whether it is in proportion for what is expected requires clinical experience. The Wells score was developed mainly for high-risk populations. In primary care, DVT should only excluded with both a negative Wells score and D-dimer testing. If there is significant clinical doubt, then referral on for DVT ultrasound should probably be requested.
3. What investigations should be done in patients presenting with DVT to establish if there is any underlying risk factor or disease? How strong is the association with cancer and to what extent should this be pursued?
In patients with a clear DVT-provoking risk factor, such as after surgery, the pick-up rate for further investigations for cancer will be low and probably not cost-effective.
There is undoubtedly an association with underlying cancer in patients who present with spontaneous DVT, over the age of 45. Historical series suggested cancer was present in around 10% of all individuals with spontaneous DVT, although in more recent studies the figure seems to be lower at around 4%.3 The value of investigations such as CT scanning for all DVT patients, without any red flag cancer symptoms, is not thought to be cost effective, as it does not seem to improve survival or down-staging of cancer at discovery. Updated NICE guidance now advises: ‘Do not offer further investigations for cancer to people with unprovoked DVT unless they have relevant clinical symptoms or signs.’2
However, all patients presenting with a unprovoked DVT should have a screening history and basic physical examination to check for underlying cancer or red flag symptoms. If there are symptoms or signs then the clinician should request focused investigations. For example, a history of altered bowel habit may require colonoscopy or a breast lump triple assessment via the breast clinic.
Patients with an unprovoked VTE should be screened for anti-phospholipid syndrome as this will affect anticoagulation choice, the need for other anti-thrombotics, the duration and dose of anticoagulant therapy. Testing is affected by the presence of a new thrombosis and also some anticoagulation. Inherited thrombophilia testing is rarely indicated as it is unlikely to affect patient management. It should be considered in those under the age of 40, with a personal history of thrombosis and where the outcome would affect their ongoing clinical management.4 Seek specialist haematology advice prior to performing inherited thrombophilia testing.
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Professor Gerry Stansby is professor of vascular surgery and honorary consultant vascular surgeon, and Dr Kathryn Musgrave is consultant haematologist and honorary senior clinical lecturer, both at Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University Medical School
