Ruling out DVT using the Wells rule and a D-dimer test

The development of a clinical prediction guide, from inception to use in everyday practice, is often a long and winding journey. In a linked paper, Geersing and colleagues (doi:10.1136/bmj.g1340) re-evaluate the Wells rule,1 which aids in the assessment of patients with suspected deep vein thrombosis (DVT) and was initially conceived almost 20 years ago.2

To understand how this study advances the specialty, consider the case of a 50 year old man presenting with a five day history of calf pain and swelling that began after he felt a sudden “popping” in the calf. Physical examination shows tenderness just below the popliteal fossa. Current diagnostic algorithms recommend determining a pretest probability for DVT, which can be done by clinical acumen or with a quantitative clinical prediction guide, such as the Wells rule. This patient would initially be assigned a Wells score of 2 (calf swelling, localised tenderness) that would be downgraded to zero if an astute clinician believed this patient had plantaris muscle tendon rupture as a “more likely alternative diagnosis.” The next step would be D-dimer testing, an index of thrombin generation, which in …