Revisiting the Past Strengthens the Present: An Evidence-Based Medicine Approach for the Diagnosis of Deep Venous Thrombosis

The clinical diagnosis of venous thrombosis is inaccurate because the clinical findings are both insensitive and nonspecific (1). The specificity of clinical diagnosis is low because the symptoms or signs can all be caused by nonthrombotic disorders. Nevertheless, the clinical findings are an important, if not crucial, adjunct to objective diagnostic testing (2). The clinical presentation can be used to stratify patients into 3 categories with a low to moderate to high pretest probability of deep venous thrombosis (2). Combining the pretest probability with objective noninvasive testing of the lower extremity improves the diagnostic outcome. If the clinical probability is low and a noninvasive test result is negative, the post-test probability is sufficiently low to exclude the diagnosis of deep venous thrombosis. If the findings of the pretest probability and the noninvasive test result are discordant, further testing is required (2). Since the pretest probability plays a pivotal role in test selection and interpretation, a well-recorded history and careful physical examination are crucial parts of the diagnostic pathway.

The next step in developing an evidence-based approach is to understand the natural history of deep venous thrombosis. Is embolic risk conditioned by location of deep venous thrombosis (3, 4)? The practical answer is yes. Distal (calf) deep venous thrombosis poses a low risk for embolization, in contrast to the high risk with proximal (thigh) thrombi (3). Proximal venous thrombosis requires antithrombotic therapy. With deep venous thrombosis confined to the calf, it is safe to perform serial noninvasive testing and use antithrombotic therapy only for patients whose thrombus subsequently extends into the thigh (3, 5). When deep venous thrombosis is suspected clinically and confirmed by objective testing, 70% or more of patients have deep venous thrombosis in the popliteal or more proximal veins (6-9). …