Palmetto Health Family Medicine Residency, Department of Family and Preventive Medicine, University of South Carolina School of Medicine, Columbia (Dr. Bornemann); Contra Costa Family Medicine Residency, Department of Family and Community Medicine, University of California San Francisco School of Medicine (Drs. Jayasekera, Bergman, and Ramos); Department of Family Medicine, University of Wisconsin School of Medicine and Public Health, Madison (Dr. Gerhart) paul.bornemann@uscmed.sc.edu
The authors reported no potential conflict of interest relevant to this article.
DVT is a relatively rare occurrence in the ambulatory setting. However, patients who present with a painful, swollen lower extremity are much more common, and DVT must be considered and ruled out in these situations.
Although isolated distal DVTs that occur in the calf veins are usually self-limited and have a very low risk of embolization, they can progress to proximal DVTs of the thigh veins up to 20% of time.58,59 Similarly, thrombophlebitis of the superficial lower extremity veins rarely embolizes, but can progress to a proximal DVT, especially if large segments are involved or if the segments are within 5 cm of the junction to the deep venous system.59 The risk of missing a proximal leg DVT is high because embolization occurs up to 60% of the time if the DVT is left untreated.60
The current standard for diagnosis of DVT is the lower extremity Doppler ultrasound examination, but obtaining same-day Doppler evaluations can be difficult in the ambulatory setting. In these instances, the American College of Chest Physicians (ACCP) recommends that even low-risk patients receive anticoagulation pending the evaluation if it cannot be obtained in the first 24 hours.59 This approach not only increases the cost of care, but also exposes patients—many of whom will not be diagnosed with thrombosis in the end—to the risks of anticoagulation.
D-dimer blood tests have drawbacks, too. While a negative high-sensitivity D-dimer blood test in a patient with a low pre-test probability of DVT can effectively rule out a DVT, laboratory testing is not always immediately available in the ambulatory setting either.61 Additionally, false-positive rates are high, and positive D-dimer exams still require evaluation by Doppler ultrasound.
Given these limitations, performing an ultrasound at the bedside or in the exam room can allow for more timely and cost-effective care. In fact, research shows that a limited ultrasound, called the 2-region compression exam, which follows along the course of the common femoral vein and popliteal vein only, ignoring the femoral and calf veins, is highly accurate in assessing for proximal leg DVTs. As such, it has been adopted for POCUS use by emergency medicine physicians.62
Multiple studies show that physicians with minimal training can perform the 2-region compression exam with a high degree of accuracy when full-leg Doppler ultrasound was used as the gold standard.63,64 In these studies, hands-on training times ranged from only 10 minutes to 5 hours, and the exam could be performed in less than 4 minutes. A systematic review of 6 studies comparing emergency physician-performed ultrasound with radiology-performed ultrasound calculated an overall sensitivity of 0.95 (95% CI, 0.87-0.99) and specificity of 0.96 (95% CI, 0.87-0.99) for those performed by emergency physicians.65
The main concern with the 2-region compression exam is that it can miss a distal leg DVT. As stated earlier, distal DVTs are relatively benign and tend to resolve without treatment; however, up to 20% can progress to become a dangerous proximal leg DVT.58 Researchers have validated several methods by prospective trials to address this limitation.
Point-of-care ultrasound screening for abdominal aortic aneurysm can be performed in less than 4 minutes.
Specifically, researchers have demonstrated that patients with a low pre-test probability of DVT per the Wells scoring system could have DVT effectively ruled out with a single 2-region compression ultrasound without further evaluation.66 In another study, researchers evaluated all patients (regardless of pretest probability) with a 2-point compression exam and found that those with negative exams could be followed with a second exam in 7 to 10 days without initiating anticoagulation. If the second one was negative, no further evaluation was needed.67,68
And finally, researchers demonstrated that a negative 2-point compression ultrasound in combination with a concurrent negative D-dimer test was effective at ruling out DVT, regardless of pre-test probability.69,70
A preferred approach
Given this data and the fact that in the ambulatory setting it is often easier and faster to perform a 2-region compression examination than to obtain a D-dimer laboratory test or a formal full-leg Doppler ultrasound, what follows is our preferred approach to a patient with suspected DVT in the outpatient setting (FIGURE 10).
We first assess pre-test probability using the Wells scoring system. We then perform the 2-region compression ultrasound. If the patient has low pre-test risk according to the Wells score, we rule out DVT. If the patient has moderate or high risk with a negative 2-region compression ultrasound, the patient gets a D-dimer test. If the D-dimer test is negative, we rule out DVT. If the D-dimer test is positive, we schedule the patient for a repeat 2-region compression ultrasound in 7 to 10 days. If at any time the 2-region compression evaluation is positive, we treat the patient for DVT.
CORRESPONDENCE Paul Bornemann, MD, Palmetto Health Family Medicine Residency, Department of Family and Preventive Medicine, University of South Carolina School of Medicine, 3209 Colonial Drive, Columbia, SC 29203; paul.bornemann@uscmed.sc.edu.
