Evaluation of d-dimer and the diagnosis of suspected deep vein thrombosis Wells PS, Anderson DR, Rodger M, et al. N Engl J Med 2003;349:1227-35

AbstractConclusionk/ST>The combination of a d-dimer assay and a clinical prediction model of the possibility of deep venous thrombosis (DVT) can safely reduce the number of ultrasound examinations required in the evaluation of patients with possible DVT.Summaryd-dimer fragments are produced during degradation of fibrin clots, and suggest the presence of thrombosis. Different assays vary in their sensitivity for detection of d-dimer and in their ease of use and expense. It is postulated that d-dimer assays with high negative predictive values for DVT may be useful in the evaluation of patients with possible DVT, perhaps permitting avoidance of ultrasound testing in some patients with a negative assay. It has also been shown that a clinical probability scoring system can be used, along with a single negative ultrasound examination, to rule out DVT in patients whose probability score suggests a low likelihood of DVT.Outpatients with suspected lower extremity DVT were categorized as likely or unlikely to have DVT. Patients were then randomly assigned to undergo ultrasonography alone (control group, n = 530) or d-dimer testing (d-dimer group, n = 569) followed by ultrasonography, unless the d-dimer test was negative and the patients' clinical probability scores suggested they were unlikely to have DVT. In these cases duplex scanning for DVT was not performed. d-dimer testing was performed with the SimpliRED assay (Agen Biomedical) or IL test (Instrumentation Laboratory).The prevalence of DVT was 15.7%. In patients in whom DVT was ruled out with the initial diagnostic strategy, over the next 3 months there were two confirmed venous embolic events in the d-dimer group (0.4%) and six in the control group (1.4%; P = .16). d-dimer testing lowered the use of ultrasonography from a mean of 1.34 tests per patient in the control group to a mean of 0.78 tests per patient in the d-dimer group (P = .008). Thirty-nine percent of patients in the d-dimer group did not require ultrasound imaging.CommentThis study indicates that it is possible to safely omit venous ultrasound studies in highly selected patients with a low probability of DVT. Implementation of this protocol may allow vascular laboratories to reduce after-hours venous duplex studies and to improve working conditions and retention of vascular technologists