The value of adding impedance plethysmography to 125I-fibrinogen leg scanning for the detection of deep vein thrombosis in high risk surgical patients: A comparative study between patients undergoing general surgery and hip surgery

The clinical value of adding impedance plethysmography (IPG) to 125 I-fibrinogen leg scanning was evaluated and compared in 630 patients who had general surgical procedures and 385 patients who had hip surgery. Patients were screened by both tests and venography was performed if either test was positive to determine a) the frequency with which proximal VT, confirmed by venography, was detected by IPG but not by leg scanning, and b) the positive predictive value of these tests used either alone or in combination. Either the IPG or leg scan result was abnormal in 67 of 630 general surgical patients (11%) and in 158 of 385 hip surgery patients (41%). The positive predictive values of the tests in general surgical and hip surgery patients was 79% and 86% respectively for the leg scan alone, 33% and 90% for IPG alone and 87% and 95% when both the leg scan and IPG were positive. The addition of IPG to leg scanning in general surgical patients identified only 1 addition patient with proximal vein thrombosis (0.2%) whereas in hip surgery patients the addition of IPG identified 25 additional patients with proximal vein thrombosis (6%). It is concluded that the addition of IPG to leg scanning is not useful among general surgical patients but is of substantial clinical value in hip surgery patients.