1. The Wells DVT criteria are a validated clinical model for estimating pre-test probability of DVT.
2. D-dimer testing in outpatients can help inform the need for venous ultrasonography in the diagnosis of DVT.
Original Date of Publication: September 25, 2003
Study Rundown: Deep vein thrombosis (DVT) is a condition where blood clots form in the deep venous system. While DVTs most frequently occur in the lower extremities, they may also develop in the upper extremities and other deep veins, such as the portal vein. Patients with DVT often present with pain, swelling, and erythema in the affected extremity. Pulmonary embolism is a concerning and potentially life-threatening complication of DVT, as pieces of thrombus may embolize to the lungs. As a result, patients with DVT are often treated with anticoagulants or, in certain circumstances, mechanical vena cava filters.
Originally developed in 1995, the Wells DVT criteria are used to determine a patient’s pre-test probability of having a DVT. These criteria have been subsequently refined and included in an algorithm to guide diagnostic evaluation for DVT using D-dimer testing and venous ultrasonography. This study was published in 2003 and helped elucidate the role of D-dimer in evaluating patients with suspected DVT. In summary, the D-dimer test had a negative predictive value of 99.1% (95%CI 96.7-99.9) in patients with low pre-test probability of DVT. In patients likely to have a DVT, its negative predictive value was 89.0% (95%CI 80.7-94.6). Thus, D-dimer testing can be used to rule out DVT in patients with low likelihood of thrombus based on clinical assessment.
In-Depth [randomized, controlled study]:
The Wells DVT criteria
|Bedridden recently >3 days or major surgery within 4 weeks|
|Calf swelling >3 cm compared to the other leg (measured 10 cm below tibial tuberosity)|
|Collateral (nonvaricose) superficial veins present|
|Entire leg swollen|
|Localized tenderness along deep venous system|
|Pitting edema, greater in symptomatic leg|
|Paralysis, paresis, or recent plaster immobilization of the lower extremity|
|Previously documented DVT|
|Alternative diagnosis to DVT as likely or more likely|
|≥2 indicates that probability of DVT is likely<2 indicates that probability of DVT is unlikely|
In this study, a total of 1096 outpatients who presented with a suspected DVT were first assessed using the clinical model to determine their pre-test probability of DVT (i.e., likely or unlikely). They were then randomized to the control group (i.e., ultrasonography) or to the intervention group (i.e. D-dimer and ultrasonography). There were no significant differences between the two groups in terms of thromboembolic events encountered in follow-up at 3 months. The D-dimer group was associated with significantly lower use of venous ultrasonography, compared to the control group. In patients unlikely to have DVT, the D-dimer test had a negative predictive value of 99.1% (95%CI 96.7-99.9). In patients likely to have DVT, the D-dimer test had a negative predictive value of 89.0% (95% CI 80.7-94.6).
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