Screening for lower extremity deep venous thrombosis. An improved plethysmographic and Doppler approach.

Noninvasive screening of the lower extremities for deep vein thrombosis was performed bilaterally on 1,118 patients. Impedance plethysmography alone was used in 868. Venography in 135 revealed an accuracy of 88%, with a false-negative rate of 5.3% and a false-positive rate of 18.6%. A combined ultrasonic Doppler and modified impedance technic was used in 250 patients. Venography in forty revealed an accuracy of 95%, with a false-positive rate of 10% and no undetected thrombi. The combined technic, emphasizing the more accurate modality in three anatomic areas, has proven sensitive, specific, and reliable as a screening test for deep venous thrombosis.