Turkstra and colleagues espouse an untenable position: that a positive result on ultrasonography for deep venous thrombosis of the thigh is false if pulmonary embolism is not documented and that asymptomatic deep venous thrombosis therefore need not be treated in the absence of pulmonary embolism. Untreated symptomatic deep venous thrombosis has a historical mortality rate of 12% to 37% [1]; in asymptomatic, high-risk patients, the mortality rate is 1% to 5% [2]. Although the handful of patients not treated in this study did not develop pulmonary embolism or die, the standard of care mandates anti-coagulation for deep venous thrombosis of the lower extremity, including the calf [3]. Although ultrasonography is less sensitive below the knee, it can identify deep venous thrombosis of a calf vein [4]. Imaging below the knee is an essential component of ultrasonography of the lower extremity.

The authors confirm well-known data: 1) Forty percent to 60% or more of patients with pulmonary embolism have negative results on noninvasive studies for deep venous thrombosis [4]; 2) results of such studies are negative in 40% to 70% of high-risk patients without signs or symptoms of deep venous thrombosis compared with venography [4]; and 3) 50% to 65% of patients with proven deep venous thrombosis have asymptomatic pulmonary embolism [5]. Because deep venous thrombosis and pulmonary medicine represent the continuum of venous thromboembolic disease, a positive result on noninvasive testing has been established as a surrogate for pulmonary embolism and the justification for its treatment. The sensitivity and specificity of ultrasonography is a measure of the method's ability to detect deep venous thrombosis and is appropriately evaluated by venography of the lower extremity. Turkstra and colleagues described the correlation between ultrasonographically documented deep venous thrombosis and pulmonary embolism in patients suspected of having pulmonary embolism; they did not describe the sensitivity and specificity of lower-extremity ultrasonography.

Treatment of deep venous thrombosis reduces the incidence of recurrent deep venous thrombosis, the postphlebitic syndrome, pulmonary embolism, and death from venous thromboembolism. A person with a positive result on a noninvasive study of the legs must receive anticoagulation [3].