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 de ep-vein thrombosis (DVT) but has poor sensitivity for isolated calf DV T, some of which can extend to the proximal veins and result in clinic ally significant pulmonary emboli. The intent of this study was to det ermine the long-term outcome of outpatients with negative VDS and to a ssess 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 pla sma determination of D-dimer, prothrombin fragment 1.2, and thrombin-a ntithrombin complex. Additionally, patients with a negative VDS were f ollowed for 6 months to determine the frequency of subsequent venous t hrombosis. Of 207 patients seen in our vascular laboratory, 171 had ei ther 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 diag nosis of DVT and were superior to the prothrombin fragment 1.2 levels. Symptomatic venous thromboembolism occurring after negative VDS is un common. D-dimer and thrombin-antithrombin levels have equal utility as diagnostic tests for DVT.