Evaluation of suspected deep venous thrombosis in oncologic patients

Impedance plethysmography (IPG) and duplex scanning with color flow Doppler were performed in 100 consecutive high-risk patients with clinically suspected deep venous thrombosis. Risk factors included recent surgery (< three weeks) in 23%, malignant disease in 91%, clotting abnormalities in 32%, and limited activity in 70%. Lower limb findings of either edema, calf tenderness, or both occurred in 92%. There was agreement between the two tests in 76 patients (29 positive and 47 negative). In 12 patients the IPG was positive and the duplex negative. Four of these had extensive pelvic disease, 2 had lung cancer with an obstructive profile, and 2 had heart failure, all of which are known to cause false-positive IPG results. In the other 12 patients the IPG was negative and the duplex positive; however, 3 of these patients had nonocclusive thrombi, 5 had pelvic disease, and 1 had a hemiparesis of the involved lower limb. In 15 patients (11 with positive duplex studies and 4 with negative) a venogram was obtained and confirmed the results. All patients were followed up clinically and none developed complications suggesting inaccurate duplex results. In conclusion, the IPG is of limited utility in this population with a sensitivity of 71%, specificity of 80%, and false-negative rate of 29% when duplex Doppler and clinical outcome are used as the standard. Where available, duplex Doppler should be preferred for evaluation of suspected deep venous thrombosis in patients with extensive medical disease.