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Should D-Dimer Testing Guide the Duration of Anticoagulation After Unprovoked VTE?

Patients with abnormal D-dimer results benefited from extended anticoagulation, but we still don’t know the overall value of D-dimer testing in guiding decision making after 3 months of standard anticoagulation therapy.

Experts still debate the optimal duration of anticoagulation therapy after a venous thromboembolism (VTE) event without a clear precipitant. Can D-dimer testing identify those patients who benefit from prolonged anticoagulation?

Researchers in Italy conducted a study involving 608 adults (mean age, 63; 52% men) who had been treated with warfarin or acenocoumarol for 3 months after apparently unprovoked, symptomatic VTE. D-dimer testing was done 1 month after subjects stopped anticoagulation therapy. Those with abnormally elevated D-dimer results (223 patients) were randomized to resume anticoagulation therapy (103) or to remain off it (120); those with normal D-dimer levels (385 patients) did not continue anticoagulation therapy. Mean follow-up was 1.4 years.

Among subjects with abnormal D-dimer levels, recurrent VTE was significantly more common in the non-resumption group than in the resumption group (15% vs. 3%; adjusted hazard ratio, 4.26; 95% CI, 1.23–14.6). Among subjects with normal D-dimer levels, the incidence of recurrent VTE was 6%, not significantly higher than in the elevated D-dimer group that resumed anticoagulation. The only major bleeding event occurred in a patient in the resumption group.

Comment: Interpreting these findings is difficult because the threshold for an abnormal D-dimer result was not defined and because D-dimer testing was delayed until after subjects had stopped anticoagulation therapy for 1 month. More important, the data do not show whether a strategy of continuous anticoagulation therapy for everyone in the trial would have been better than a strategy of using D-dimer testing to guide decisions about anticoagulation. Without that evidence, D-dimer testing after 3 months of anticoagulation therapy in patients with apparently unprovoked VTE remains a strategy of uncertain value.

— Harlan M. Krumholz, MD, SM

Published in Journal Watch Cardiology October 25, 2006

Citation(s):

Palareti G et al. for the PROLONG Investigators. D-dimer testing to determine the duration of anticoagulation therapy. N Engl J Med 2006 Oct 26; 355:1780-9.

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