D-dimer testing based on clinical pretest probability for deep vein thrombosis (DVT) is safe and reduces diagnostic testing compared with testing all patients. Researchers randomly assigned 1,723 outpatients presenting for the first time with symptoms of DVT to either selective testing (D-dimer testing for patients with low or moderate clinical pretest probability of DVT or venous ultrasonograpy without D-dimer testing in patients with high clinical pretest probability) or uniform testing (testing for all patients presenting with symptoms).
Since D-dimer testing is sensitive but not specific for diagnosing DVT, the authors hypothesized that selective testing may be a more efficient strategy than testing all patients. They found that selective testing reduced a proportion of patients who required ultrasonography, and resulted in 21.8 percent fewer patients requiring D-dimer testing.
The incidence of venous thromboembolism at three months was 0.5 percent in both study groups, which is considered an acceptable threshold. The authors suggest further studies to determine if a selective strategy can be applied to patients who present with suspected recurrent DVT or pulmonary embolism.