Low risk of subsequent deep-venous thrombosis in patients with a negative venous duplex scan

Venous duplex scanning (VDS) is sensitive and specific for proximal deep-vein thrombosis (DVT) but has poor sensitivity for isolated calf DVT, some of which can extend to the proximal veins and result in clinically significant pulmonary emboli. The intent of this study was to determine the long-term outcome of outpatients with negative VDS and to assess the accuracy of three biochemical markers of hypercoagulability for the detection of DVT. Consecutive ambulatory patients referred to our vascular laboratory with a question of lower extremity DVT had plasma determination of D-dimer, prothrombin fragment 1.2, and thrombin-antithrombin complex. Additionally, patients with a negative VDS were followed for 6 months to determine the frequency of subsequent venous thrombosis. Of 207 patients seen in our vascular laboratory, 171 had either a single negative VDS or two negative studies (done 24-72 h apart). Follow-up of 161 patients for 6 months showed no evidence of venous thromboembolism. The remaining 10 patients died from other causes or had alternative diagnoses made to explain their symptoms. The D-dimer and thrombin-antithrombin complex had equal test accuracy for the diagnosis of DVT and were superior to the prothrombin fragment 1.2 levels. Symptomatic venous thromboembolism occurring after negative VDS is uncommon. D-dimer and thrombin-antithrombin levels have equal utility as diagnostic tests for DVT.