Measurement of D-dimer concentrations may help clinicians predict who is at high risk of recurrent venous thromboembolism (VTE) after stopping anticoagulant therapy. Recurrent VTE occurs in as many as 30% of patients who discontinue therapy. Those at highest risk include patients who are male, are obese (>30 kg/m2), and had a proximal (vs distal) deep vein thrombosis. A recent prospective study of 608 patients evaluated the rate of recurrence after 3 months of oral anticoagulant therapy. Therapy was stopped after 3 months, then D-dimer levels were measured a month later. Patients with normal levels (n = 385) did not resume therapy. Patients with high levels (n = 223) were randomized to resume therapy or remain off anticoagulants. After an average of 1.4 years of follow-up, recurrence rates were 6.2% in the group with normal levels, 1.9% in the group that resumed therapy, and 15% in the group with high levels who remained off therapy. The authors concluded that high D-dimer levels predict high risk of recurrent VTE, and this risk can be minimized by restarting warfarin therapy.
Long-term therapy with anticoagulants lowers recurrent VTE risk but is associated with a 1% to 3% risk of major bleeding. Identifying patients with a low risk of recurrence is important in order to safely discontinue therapy as soon as possible. Current recommendations for a first episode of unprovoked VTE call for 6 to 12 months of therapy. The results of this study suggest that use of the D-dimer test may provide an alternate approach to therapy, although further evaluation is necessary to confirm safety and efficacy.
Dr. Garrett is a clinical pharmacist practitioner at Cornerstone Health Care in High Point, NC.