Vascular-laboratory diagnosis of clinically suspected acute deep-vein thrombosis

Doppler ultrasound, impedance plethysmography, and contrast venography were performed in 207 lower limbs suspected of harbouring deep-venous thrombosis, to clarify the diagnostic value and limitations of the non-invasive methods. Doppler ultrasound and impedance plethysmography were accurate in 96% and 95% of normal limbs, respectively. In limbs with venographic evidence of thrombosis requiring treatment, Dopper ultrasound and impedance plethysmography correctly detected thrombosis in 60% and 97%, respectively. Doppler ultrasound was 97% accurate in recognising chronic venous insufficiency. Impedance plethysmography was incorrectly positive in 74% of limbs with chronic venous insufficienv cy which had no venographically detected thrombosis. These findings suggest that, for the accurate diagnosis of clinically suspected deep-vein thrombosis, venography is necessary only in patients with chronic venous insufficiency who have normal Doppler ultrasound tests and abnormal impedance plethysmograms and in patients with abnormal cardiac haemodynamics. In this series, 86% of limbs would have been spared venography had non-invasive tests been used. Venography, however, remains the standard test for the detection of minor calf-vein thrombosis. A diagnostic and therapeutic schema is proposed.