A prospective study comparing duplex scan and venography for diagnosis of lower-extremity deep vein thrombosis.

This study was designed to compare duplex scanning with contrast venography for the diagnosis of acute deep vein thrombosis of the lower extremity, both at the femoropopliteal (above-knee) and tibioperoneal (below-knee) levels. A total of 216 patients with 220 limbs suspected of acute deep vein thrombosis underwent duplex scanning followed within 24 h by ascending venography. The two studies were interpreted independently by two physicians who were blinded to the results of the corresponding alternative study. Venography was positive for deep vein thrombosis in 44.5% of cases (98/220). Duplex scanning was inadequate at the above-knee level in two cases (0.9%) and at the below-knee level in 17 cases (7.7%). Sensitivity and specificity of duplex scanning at above-knee level were 98.7% and 100% respectively while corresponding values were 85.2% and 99.2% at below-knee level. By excluding technically inadequate duplex studies, the sensitivity at below-knee level was clearly improved (93.8%). It is concluded that with meticulous technique, duplex scanning is highly accurate in diagnosing acute deep vein thrombosis of symptomatic lower extremities, avoiding contrast venography in over 90% of the cases, even at the tibioperoneal level.