Comparative value of tests for the diagnosis of venous thrombosis
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AbstractThe clinical diagnosis of venous thrombosis lacks sensitivity and specificity. Venography is recognized as the diagnostic reference standard but is invasive and associated with patient morbidity.125I‐fibrinogen leg scanning is sensitive to calf vein thrombosis but is relatively insensitive to femoral vein thrombosis and does not detect iliac vein thrombosis. This test is most useful as a screening test in high‐risk medical and surgical patients. The test may be falsely positive at the site of hematoma, and because of this, it has serious limitations in patients undergoing knee and hip surgery. Leg scanning also has limitations when used to diagnose patients with suspected venous thrombosis because it may take up to 72 hours to obtain a positive result. Impedance plethysmography (IPG), a noninvasive technique, is sensitive and specific for thrombosis involving the popliteal, femoral, and iliac veins. Combined with125Ifibrinogen leg scanning, this test has considerable potential as a screening test in patients undergoing hip surgery. The combined use of IPG and leg scanning has also been shown to be highly accurate for the diagnosis of clinically suspected venous thrombosis, and this approach offers a less invasive alternative to venography in these patients. The Doppler ultrasound flowmeter, like the IPG, is sensitive to popliteal and more proximal vein thrombosis but is relatively insensitive to calf vein thrombosis. The interpretation of the results of this test is more subjective and much more dependent upon the expertise of the examiner than is the IPG. A number of other techniques, including image scanning, and themography, are under investigation but require further evaluation before they can be recommended in the management of patients with venous thromboembolism.
