50% of women with unprovoked VTE could be spared life-long anticoagulation

Patients with an unprovoked VTE have a high risk of recurrent VTE (about 30% at 5 years). Thus, guidelines suggest life-long anticoagulation for these patients.¹ However, among these patients, the risk of recurrent VTE varies considerably depending on patient factors (e.g., age, BMI, evidence of venous stasis changes on physical exam) and laboratory factors (e.g., D-dimer level). Therefore, clinicians often face the challenge of identifying which patients can safely stop anticoagulation after 3 to 6 months of therapy and which patients should continue anticoagulation life-long.

This large, prospective cohort study, involving 44 centers in 7 countries, validated the HERDOO2 score. About half of the women with an unprovoked VTE were classified as having a low risk of recurrent VTE and could discontinue anticoagulation. Therefore, life-long anticoagulation, as suggested by the guidelines, could be avoided in women with a low HERDOO2 score.

This study has some limitations. The definition of “unprovoked” included patients who had VTE associated with a minor or weak risk factor (e.g., estrogen therapy). This group generally has a lower risk of VTE recurrence compared with patients with no risk factors and their inclusion likely reduced the overall recurrence rate. Second, the HERDOO2 rule was applied in women after 5 to 12 months of treatment rather than the usual first decision point at 3 months. It is unclear if the score is still valid if applied at 3 months. In addition, the duration of follow-up was limited to 1 year. Finally, a single D-dimer test at a low cutoff value was used for all patients. Other studies have suggested repeating a D-dimer level one month after discontinuing anticoagulant therapy to ensure it remains negative.² Furthermore, there are many different D-dimer assays; the HERDOO2 results with the VIDAS assay should not be applied to another assay without validation either in the literature or locally.

The HERDOO2 score does not apply to patients with any of these risk factors at the time of the VTE: surgery within the past 4 weeks, immobilization >3 days, leg injury, active cancer, high-risk thrombophilia, or pregnancy.

When talking with women with an unprovoked VTE who have received anticoagulation for 5 to 12 months, management options now include stopping the anticoagulant if the HERDOO2 score is 0 or 1 (using the VIDAS D-dimer assay), switching to a prophylactic dose of a direct oral anticoagulant (DOAC) (e.g., rivaroxaban, apixaban), which provides a high level of protection with low bleeding risk, or continuing standard dose anticoagulants (if there are other risk factors that are not included in the HERDOO2 score or due to patient preference).

Doctor, I have finished 6 months of anticoagulant treatment. Can I stop now?

Men: You have a high risk of recurrence; therefore, we recommend that you continue anticoagulation to protect you from having another blood clot.

Women: You may be able to stop your anticoagulant. We will use a score that includes a combination of your age, height and weight, the appearance of the skin on your legs, and the results of a blood test to determine if it is safe for you to stop.

1. Kearon C, Akl EA, Comerota AJ, Prandoni P, et al. Antithrombotic therapy for VTE disease: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012; 141(2 Suppl): e419S-e496S.

2. Kearon C, Spencer FA, O’Keeffe, Parpia S, Schulman S, Baglin T, Stevens SM, Kaatz S, Bauer KA, Douketis JD, Lentz SR, Kessler CM, Moll S, Connors JM, Ginsberg JS, Spadafora L, Julian JA; D-dimer Optimal Duration Study Investigators. Ann Intern Med. 2015; 162 (1): 27-34.