From the Guidelines
The Wells score is a crucial tool in determining the need for D-dimer testing in patients with suspected deep vein thrombosis (DVT) or pulmonary embolism (PE), with a score of 2 or higher indicating "DVT likely" and warranting direct imaging or D-dimer testing, while a score of 1 or less indicates "DVT unlikely" and should be followed by D-dimer testing. The Wells score helps stratify patients based on clinical probability, allowing clinicians to avoid unnecessary imaging in low-risk patients with negative D-dimer results 1. This approach is effective because D-dimer has high sensitivity but poor specificity, meaning a negative result helps rule out thrombosis in low-risk patients, while a positive result in high-risk patients may not add value beyond what the clinical assessment already suggests 1.
Key Points to Consider
- The Wells score is used in conjunction with D-dimer testing to evaluate patients with suspected DVT or PE 1.
- A Wells score of 2 or higher indicates "DVT likely" and warrants direct imaging or D-dimer testing, while a score of 1 or less indicates "DVT unlikely" and should be followed by D-dimer testing 1.
- The Wells score helps stratify patients based on clinical probability, allowing clinicians to avoid unnecessary imaging in low-risk patients with negative D-dimer results 1.
- D-dimer has limited utility in hospitalized patients and in certain patient populations (postsurgical, pregnancy) due to the high frequency of positive D-dimer results with standard thresholds 1.
Clinical Application
The Wells score is a valuable tool in clinical practice, as it helps clinicians to quickly and accurately assess the likelihood of DVT or PE in patients. By using the Wells score in conjunction with D-dimer testing, clinicians can optimize resource utilization and reduce unnecessary radiation exposure from imaging studies 1. However, it is essential to consider the limitations of the Wells score and D-dimer testing, particularly in certain patient populations, and to use clinical judgment when interpreting the results 1.
Evidence-Based Recommendation
The Wells score should be used to determine the need for D-dimer testing in patients with suspected DVT or PE, with a score of 2 or higher indicating "DVT likely" and warranting direct imaging or D-dimer testing, while a score of 1 or less indicates "DVT unlikely" and should be followed by D-dimer testing. This approach is supported by the most recent and highest quality evidence, including the 2018 American Society of Hematology guidelines for management of venous thromboembolism 1.
From the Research
Role of the Wells Score in Deciding Whether to Test for D-dimer
The Wells score is a clinical decision rule used to assess the likelihood of deep vein thrombosis (DVT) or pulmonary embolism (PE) in patients with suspected venous thromboembolism. The score is used in combination with D-dimer testing to determine the need for further diagnostic testing.
Combination of Wells Score and D-dimer Testing
- The Wells score is used to stratify patients into different risk categories, with higher scores indicating a higher likelihood of DVT or PE 2.
- D-dimer testing is then used to further evaluate patients with a low to moderate Wells score, as a negative D-dimer result can safely exclude DVT or PE in these patients 2, 3.
- The combination of the Wells score and D-dimer testing has been shown to be effective in reducing the need for computed tomography (CT) scanning in patients with suspected PE 2.
- A study found that using the Wells score with a D-dimer threshold of 1000 μg/L in patients with no signs of DVT or PE, and 500 μg/L in patients with one or more of these signs, could exclude PE without CT scanning in 36% of patients, with a false-negative rate of 1.2% 2.
Safety and Efficiency of D-dimer as a Stand-Alone Test
- Some studies have suggested that D-dimer testing may be used as a stand-alone test to rule out DVT, particularly in outpatients with a low pretest probability of DVT 3.
- However, the safety and efficiency of this approach are still being debated, and further studies are needed to confirm its effectiveness 3, 4.
- A study found that using D-dimer as a stand-alone test to rule out DVT resulted in a failure rate of 1.8%, with most misdiagnosed cases being distal DVTs 3.
Clinical Usefulness of D-dimer Testing
- D-dimer testing has been integrated into sequential diagnostic strategies, including those using pretest clinical probability assessment and imaging techniques 4.
- The diagnostic yield of D-dimer testing is affected by the choice of assay, patient characteristics, and clinical setting 4, 5.
- A study found that the combination of the Wells score with either a D-dimer test or selective compression sonography had a negative predictive value of 99.0% for excluding DVT, compared to 95.0% for clinical judgment alone 5.