The Clinical Usefulness of D-Dimer Testing in Cancer Patients With Suspected Deep Venous Thrombosis

Abstract

MAJOR IMPROVEMENTS in the diagnostic management of patients with suspected deep venous thrombosis (DVT) have been achieved in the last decades. At first, the invasive procedure of venography was replaced by noninvasive tests, such as impedance plethysmography and compression ultrasonography. However, additional tests performed during a 2-week period were required to rule out adequately the diagnosis. Subsequently, it was shown for compression ultrasonography that the number of follow-up tests could be safely reduced to a single follow-up test with a 1-week interval.^1,2 Recently, further improvements have been attained by the introduction of the D-dimer test. A D-dimer test represents the level of plasma D-dimers, which are degradation products of cross-linked fibrin. Numerous studies^3,4 have investigated the accuracy of this test for the diagnosis of DVT. Since the sensitivity of the test is approximately 90% to 95% and the specificity is only 55%, the test is best suited for ruling out DVT instead of proving the presence of the disease. However, the test cannot be used as the sole test to exclude DVT, since given a sensitivity of approximately 90% to 95%, still 5% to 10% of DVTs will be missed. Therefore, the test should be used as an adjunct to other diagnostic methods. Management studies have shown that if a rapid D-dimer test is performed with ultrasonography in patients suspected of having DVT, the diagnosis can be ruled out if both test results are normal. Two large studies^5,6 have recently demonstrated that, using this strategy, the follow-up ultrasonogram and thus an extra hospital visit can be safely omitted in more than 45% of patients. A follow-up ultrasonogram is necessary to exclude an extending (calf) vein thrombosis only in the remaining patients with an abnormal D-dimer test result at referral.