Use of D-dimer to aid in excluding deep venous thrombosis in ambulatory patients

Background Duplex imaging is currently the gold standard for diagnosing deep venous thrombosis (DVT), but its nonselective use overburdens vasuclar laboratories, particularly during off hours. It is the purpose of this study to determine if a new D-dimer assay could be used as an aid in determing whether duplex imaging could be performed on an elective or emergent basis in patients with suspected DVT. Methods D-dimer levels were measured and venous duplex examinations were obtained in all patients. D-dimer assays were performed using the Tina-quant latex agglutination test (Roche Diagnostics, Mannheim, Germany). Venous duplex examinations were performed using colorflow doppler. Results Between September 1, 2002 and April 30, 2003, 148 patients were seen in the emergency department for suspected DVT. Nineteen patients (12.8%) had positive venous duplex examinations and 129 (87.2%) duplex examinations were negative. None of the 19 patients with positive venous duplex studies had D-dimer levels within of the normal range (0 to 0.49). The sensitivity, specificity, positive predictive value, and negative predictive value of the D-dimer test were 100%, 48.8%, 22.4%, and 100%, respectively. Conclusion The D-dimer test can effectively used without adjuncting risk straification as an aid in excluding the diagnosis of DVT in ambulatory patients. Its routine use could significantly reduce the need for the performance of emergent venous duplex examinations.