Lower-Extremity Venous Ultrasound in DVT-Unlikely Patients with Positive D-Dimer Test

To review the clinical data, D-dimer level and the ultrasonographic findings from complete venous ultrasound of the lower extremity in deep venous thrombosis (DVT)-unlikely patients with abnormal D-dimer test were compared to DVT-likely patients to ascertain the appropriate ultrasound examination protocol for patients in this group.

A retrospective cohort study was conducted of all patients who underwent a complete (whole leg) venous ultrasound in one 13-month period. The medical history, demographic, clinical risk factors, and ultrasonographic findings of the patients with high clinical probability for deep vein thrombosis (Wells score ≥2), along with patients with a low clinical probability of deep vein thrombosis (Wells score ≤1) but with a D-dimer level higher than the threshold (≥500 ng/ml FEU) were evaluated.

There were 96 patients in the DVT-likely group and 86 patients in the DVT-unlikely group. The indication for ultrasound examination in the DVT-unlikely group was preoperative assessment to avoid the risk of pulmonary thromboembolism. The patients in the DVT-likely group had more positive ultrasound results for DVT (15.63% vs. 5.18%, p value = 0.03) than the patients in the DVT-unlikely group. In the DVT-unlikely group, the median D-dimer level in the patients with positive ultrasound for DVT showed statistically significantly higher levels than the patients with negative ultrasound for DVT did (2208 vs. 921 ng/ml FEU, p value = 0.02). The optimal D-dimer cut-off from the receiver operating characteristics analysis shows the maximized summation of sensitivity and specificity (80% and 66.67%) at 1251 ng/ml FEU. The prevalence of acute thrombus in a thigh vein in DVT-unlikely, preoperative patients is low (1.2%).

To minimize the number of unnecessary complete venous ultrasound lower-extremity examinations, the use of a higher D-dimer cut-off level and limiting proximal or thigh vein ultrasound examinations in the preoperative patient is considered.