Reliability of Doppler and impedance techniques for the diagnosis of thrombophlebitis.

The accuracy of Doppler ultrasound and impedance diagnostic techniques for identifying deep venous thrombosis was determined by comparison with patient venograms. Those patients suspected of having deep venous thrombosis were tested by ultrasound, impedance, and venography, with venography the standard for establishing the accuracy of the noninvasive methods. The deep inspiration, the Valsalva and abdominal pressure maneuvers, and the pneumatic cuff technique were employed with the impedance tests. The incidence of false negative and false positive results were determined for each noninvasive method separately and for both methods used concurrently. When both methods were considered, the number of false positives was high; however, all cases with major thrombosis were detected in the group of patients examined. A positive result with ultrasound or impedance tests should be considered an indication to perform venography, or if venography is contraindicated, to perform other noninvasive tests.