Toolbox - Well's DVT score
Professor Gerard Stansby, professor of vascular surgery, and colleague Mr. Alex Watson offer advice on applying the Wells DVT score in practice.
The two-level Well’s DVT score is a clinical prediction tool for patients presenting with a clinical picture suspicious for venous thrombosis. Rapid assessment, early diagnosis and management of DVT reduces the morbidity and mortality of thrombosis related complications such as pulmonary embolism and post-phlebitic limb.
It is a key step in the NICE guidelines for the management of venous thromboembolic diseases and helps to guide further investigation and treatment.
A similar Wells score exists for pulmonary embolisms.
When to use it
Use in all patients presenting with signs and symptoms suggestive of possible DVT, following a thorough history and examination to rule out differential diagnoses.
- Refer to the two-level DVT Wells table, attached to this article, to generate a score of probability of DVT based on the patient’s clinical features.
- A score of 2 or more makes a DVT likely and the patient should undergo a deep venous ultrasound. If this cannot take place within four hours then a D-dimer test should be undertaken instead and the patient treated with therapeutic parenteral anticoagulation until a scan is performed.
- A score of 1 or less makes a DVT unlikely and a D-dimer test should be performed as a first-line investigation instead. This may cause some difficulties in practice if a D-dimer test is not immediately available. Solutions to this would be to consider the use of near patient testing kits which have been shown to be very reliable providing results within minutes at low cost, sending the patient up to hospital for the blood test to be carried out urgently or by developing specific care pathways with local biochemistry and courier services via the commissioning arrangements. The importance of a rapid approach to diagnosis is underscored by the fact that the recently published quality standards for venous thromboembolism diagnosis and management include completion of all investigations within 24 hours of clinical suspicion as one of the nine final published standards.1
- Positive ultrasounds confirm the diagnosis and necessitate further treatment whilst positive D-dimers necessitate further venous ultrasounds. See the algorithm attached to this article for a detailed overview of the clinical reasoning process.
- Consider alternative diagnoses in negative outcomes.
A good clinical probability score helps to stratify people into different risk categories, so that the most appropriate diagnostics pathway or treatment pathways can be followed. NICE considered all validated clinical probability scores for patients with a suspected DVT but only a few exist.
The original Wells score, sometimes called the Hamilton score, produced in 1997 gave three levels of risk – low, intermediate and high - but this was updated in 2003 to include “previously documented DVT” and simplified the outcomes to likely and unlikely.2
The Wells score was found to have a sensitivity range of 77-98% and a specificity of 37-58% meaning that between 2 to 23 out of 100 patients with a DVT will be missed if the Wells score is used alone and 42-63 out of 100 patients without a DVT will be identified as having one. Further diagnostic tests are therefore required. It is much more sensitive in cancer patients at around 96%.3 This clearly highlights that, like most scoring systems, the Wells DVT score should be used in combination with global clinical assessment by those trained in its use and not in isolation. However the Wells score still remains the best validated approach.
It was also found to be a component of the most cost-effective algorithms identified in the economic evidence.
Professor Gerard Stansby is a professor of vascular surgery at the Freeman Hospital in Newcastle
Mr. Alex Watson is a consultant of vascular surgery at the Freeman Hospital in Newcastle
1. Quality standard for diagnosis and management of venous thromboembolic disease QS29. NICE quality standard March 2013, Quality standard 2. http://guidance.nice.org.uk/QS29
2. Wells PS, Anderson DR, Rodger M, Forgie M, Kearon C, Dreyer J et al. Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis. New England Journal of Medicine. 2003; 349(13):1227-1235. (Guideline Ref ID WELLS2003A)
3. Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing. NICE clinical guideline June 2012