Defining the role of risk stratification and duplex ultrasound in the diagnosis of acute lower extremity deep vein thrombosis.

Objective: Risk stratification using the plasma D-dimer level and Wells score has been proposed as a safe strategy to rule out acute lower extremity deep vein thrombosis (DVT) and limit the use of duplex ultrasound (DUS) for low-risk patients. A widely used diagnostic protocol defining the role of pretest probability and D-dimer testing in lieu of DUS has not been reported. Our aim was to define the risk of DVT in a standard population of emergency department patients who had presented with acute lower extremity symptoms and determine the role of DUS for these patients.

Methods: Outpatients presenting to the emergency department with symptoms concerning for lower extremity DVT were prospectively enrolled. All the patients underwent whole leg DUS and clinical and laboratory assessments for DVT using the Wells criteria and plasma D-dimer testing. The patients were stratified into three groups according to the combination of their Wells score and plasma D-dimer level. The prevalence of DVT and the statistical performance of the combined Wells score and plasma D-dimer were compared.

Results: A total of 3087 patients were enrolled. Most of the patients had had a negative plasma D-dimer level and Wells score (n = 2290 patients). A total of 222 patients had had a positive plasma D-dimer level and Wells score. The overall prevalence of acute DVT in the present study was 7.3%. Of the 2290 patients with a negative Wells score and negative plasma D-dimer level, 4 had had a diagnosis of DVT (negative predictive value, 99.8%). In contrast, DVT was present in 181 of 222 patients (81.5%) with a positive Wells score and plasma D-dimer level (positive predictive value, 81.5%). The plasma D-dimer level also correlated with the DVT location, and the D-dimer levels were highest for the patients with proximal DVT.

Conclusions: The combination of a negative Wells score and negative plasma D-dimer level can safely exclude the presence of DVT. Patients with a negative Wells score and negative plasma D-dimer level are unlikely to benefit from DUS. In contrast, patients with a positive D-dimer level and positive Wells score will benefit from whole leg DUS to rule out the presence of high-risk DVT.