D-Dimer Testing for Deep Venous Thrombosis: A Metaanalysis (Clinical Report‪)‬

Deep venous thrombosis (DVT) (4) is a common condition with significant morbidity and mortality if not diagnosed and treated in a timely manner. The clinical signs and symptoms of DVT are nonspecific, and objective testing is required for diagnosis. Diagnostic imaging with contrast venography or compression ultrasonography has important limitations. Venography is invasive and expensive, is contraindicated in some patients, and requires a radiologist to perform. Compression ultrasound also requires a radiologist's interpretation and has poor sensitivity for detection of calf vein thrombosis, and serial testing is often required when the initial scan is negative. The measurement of D-dimer, degradation products of circulating cross-linked fibrin formed during activation of the coagulation system, has been studied extensively as an adjuvant test in the diagnosis of DVT. D-Dimer testing has become rapid, simple, and inexpensive, and it has the potential to detect thrombosis in any part of the venous system. If the sensitivity of the D-dimer test for DVT is consistently very high, its negative predictive value will also be high and reliably exclude the presence of disease. These are characteristics of a good "rule-out" test. As such, the use of D-dimer assays has been suggested as an initial test to rule out DVT to reduce the number of patients requiring diagnostic imaging. In 1996, our systematic review did not find sufficient evidence to support the use of D-dimer as a diagnostic test for DVT (1). However, since that time several new D-dimer assays have been introduced, and 50 studies and 8 reviews on the subject have been published (2-9). Because none of the reviews critically appraised the primary studies or discussed the potential for bias in their results, we undertook this metaanalysis of the D-dimer accuracy literature published since our last systematic review to clarify the role of the test in the diagnosis of lower extremity DVT.