Boston, MA - Assays for the fibrin-degradation product d-dimer could potentially be used to identify patients on oral anticoagulants to treat venous thromboembolism (VTE) who are at high risk for recurrence, report investigators in the October 26, 2006 issue of the New England Journal of Medicine [1].

The finding in patients who had experienced a first episode of deep-venous thrombosis or pulmonary embolism suggests that the d-dimer test "may be useful in guiding the duration of anticoagulation by helping clinicians select patients who may benefit the most from the prolongation of this demanding and risky treatment," write the authors, Dr Gualtiero Palareti (S Orsola-Malpighi University Hospital, Bologna, Italy) and colleagues.

D-dimer testing was performed in 608 such patients about a month after they went off at least three months of therapy with warfarin or acenocoumarol. The treated first VTE episode was required to have been "unprovoked," defined as not being associated conditions that might promote VTE, including pregnancy, a recent leg fracture or plaster casting, hospital-bed confinement, and cancer.

Those in whom the qualitative d-dimer assay yielded normal results remained off anticoagulation therapy, while patients with abnormal d-dimer readings were randomized either to resume or stay off oral anticoagulants.

The patients with abnormal d-dimer results who remained off anticoagulation showed a higher rate of the composite primary end point, confirmed recurrent VTE or major bleeding event, than either of the two other groups over a follow-up that lasted at least nine months and averaged 1.4 years.

The adjusted primary end-point hazard ratio (95% CI) for patients with abnormal d-dimer results who stayed off anticoagulants was 4.26 (1.23-14.6) compared with those with an abnormal test who resumed anticoagulation and 2.27 (1.15-4.46) compared with those with normal d-dimer results (p=0.02 for both differences). The hazard increases were independent of age, sex, preenrollment duration of anticoagulation therapy, type of VTE event that earned study eligibility, and the presence or absence of congenital thrombophilia.

The primary end-point risk was about the same for patients who had tested normal for d-dimer and those who tested abnormal and went back on oral anticoagulation, according to Palareti et al.

The authors note several limitations of their study that could be addressed in future trials, including its unblinded nature, its inability to clarify the role of role of d-dimer testing when it is performed either before patients go off anticoagulation or repeatedly during follow-up, its inability to define the associated bleeding risk as a sole end point, and its limitation to patients with unprovoked VTE, "since the optimal duration of anticoagulation is most uncertain in this category of patients. However, a management strategy for all groups of patients, regardless of the nature and number of their previous events, would be of great practical use."