Clinical Question: Does a normal D-dimer level in a patient at low or moderate risk rule out deep venous thrombosis (DVT)?

Setting: Outpatient (any)

Study Design: Cohort (prospective)

Synopsis: A number of recent studies have attempted to validate less invasive protocols for the evaluation of patients with thromboembolic disease. As with most of these studies, the protocol in this study begins with a clinical assessment of the risk of DVT using the validated Wells criteria, and follows up with further diagnostic testing. In this case, patients at low risk (13 percent with DVT) and moderate risk (38 percent with DVT) had a D-dimer test (Tinaquant quantitative latex agglutination test).

Patients at low and moderate risk (Wells score less than 3) and a normal D-dimer test result (n = 176, 22 percent) received no further testing. Patients with a high clinical score and a normal D-dimer level (n = 39, 5 percent) underwent ultrasonography; if the results were normal, they received no further testing. Patients with an abnormal D-dimer level (n = 597, 74 percent) underwent ultrasonography. If the results were normal, ultrasonography was repeated one week later. If those test results were normal, no further testing was done.

All patients were followed up at three months by telephone or a visit to their physician. Patients were instructed to seek care if they were symptomatic but were evaluated only if they became symptomatic. The algorithm was effective; only one of 176 patients with a low or moderate clinical risk and a normal D-dimer result had a DVT diagnosed during the three-month follow-up period. Of the 39 patients with high clinical risk and normal D-dimer result, three had a DVT diagnosed by the initial ultrasonography, and one additional patient had a pulmonary embolism at day 71 of follow-up.

Bottom Line: Patients with a normal D-dimer test result and a low or moderate clinical risk based on the Wells score have a very low risk of DVT and require no further testing. (Level of Evidence: 1b)

Used with permission from Ebell M. DVT 1% if normal D-dimer in non high-risk patients. Retrieved April 21, 2003, from: http://www.InfoPOEMs.com.