Is it safe to omit additional tests if d-Dimer is negative?
Ruth Morrison RN, BSN, CVN
August, 2006
Study: Kearon C, Ginsberg JS, Douketis J, et. al. An evaluation of D-dimer in the diagnosis of pulmonary embolism: a randomized trial. Ann Intern Med. 2006 Jun 6;144(11):812-21.
D-Dimer is a fibrin-derived fragment that is released into the circulation when cross-linked fibrin is broken down by the fibrinolytic system. Elevated levels of d-dimer are common in patients with venous thromboembolism. In several previous cohort and management studies, patients with the combination of a negative d-dimer and a low clinical suspicion of pulmonary embolism were unlikely to suffer pulmonary embolism. Prior to this study, the safety of omitting additional diagnostic testing in selected patients with suspected pulmonary embolism and a negative d-dimer test results had not been studied.
The goal of the trial was to determine if it is safe to withhold additional testing in patients with suspected pulmonary embolism (PE) and negative d-dimer test results. The trial was to test the hypothesis that patients with negative D-dimer test results who do not undergo further testing for pulmonary embolism will not have a higher frequency of venous thromboembolism during follow-up than patients who receive usual diagnostic testing and management.
The trial studied 2 subgroups of patients with suspected pulmonary embolism and negative d-dimer test results: patients with a low clinical suspicion of pulmonary embolism (group A) and those with a moderate or high clinical probability of PE who had a nondiagnostic ventilation-perfusion lung scan and no proximal deep venous thrombosis on venous ultrasonography (group B). Prior to diagnostic testing, the Wells 7-item prediction rule was utilized to categorize the patient’s clinical probability of pulmonary embolism as either low or moderate to high.
The experimental intervention for both probability groups was no further diagnostic testing for PE. The control intervention for the low probability group was a ventilation-perfusion lung scan followed by ultrasonography of the proximal deep leg veins on the same day. If the lung scan was nondiagnostic, ultrasound of the leg veins was repeated 7 and 14 days later. The control intervention for the moderate or high-probability group was ultrasonography of the proximal deep veins of the legs after 7 and 14 days.
Study duration was 6 months. At 6 months, 0 of 182 (group A) and 1 of 41 (group B) patients with no further testing had had symptomatic venous thromboembolism, compared with 1 of 185 (group a) and 0 of 41 (group B) patients with further testing. The study demonstrated that it is safe to withhold additional diagnostic testing in outpatients and inpatients with a low clinical suspicion of pulmonary embolism and a negative d-dimer test results.
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