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Thrombus
Results of the REVERSE-II study appear to validate the utility of the HERDOO2 rule to identify women who can safely stop taking anticoagulants after their first unprovoked venous thromboembolism (VTE).
Some women who were classified as low-risk according to HERDOO2 did experience VTE recurrence after they stopped taking anticoagulants.
However, their risk of recurrence was lower than that of women who were classified as high-risk and stopped taking anticoagulants.
These results were published in The BMJ.
“Patients can get very anxious trying to balance the risks of [anticoagulation] with the risks of another blood clot,” said study author Marc Rodger, MD, of Ottawa Hospital and University of Ottawa in Ontario, Canada.
“With this rule, we can confidently tell half of the women we see that they are at low risk of having another blood clot. This means they can stop taking blood thinners once their initial clot is treated, sparing them the cost, inconvenience, and risks of taking life-long medication.”
The HERDOO2 rule suggests a woman has a low risk of VTE if she has 1 or none of the following risk factors:
- HER=Hyperpigmentation, edema, or redness in either leg
- D=High levels of D-dimer in the blood
- O=Obesity (body mass index of 30 kg/m2 or more)
- O=Older age (65+).
To test the rule, Dr Rodgers and his colleagues evaluated 2785 men and women with a first, unprovoked VTE. The patients were recruited between 2008 and 2015 from 44 healthcare centers in 7 countries.
Patients who were found to be at low risk of VTE recurrence were told to stop taking anticoagulants after they completed the initial treatment for their first VTE.
For patients considered at high risk for VTE recurrence, the researchers left the decision of continuing anticoagulation to the patients and their doctors.
Low-risk patients
None of the men in this trial could be identified as low-risk using the HERDOO2 rule.
However, 631 women had a low risk of VTE recurrence according to HERDOO2. Most of these women (n=591) stopped anticoagulant therapy.
Twenty-seven low-risk women decided to continue anticoagulation, 1 patient’s physician decided she required continued anticoagulation, and 3 patients continued for “other” reasons.
Nine patients in this group were lost to follow-up.
High-risk patients
There were 2148 men and women considered at high risk for VTE recurrence. Most of these patients (n=1802) continued anticoagulation.
Of the 323 high-risk patients who stopped anticoagulation, 279 did so because of their own preference, 9 due to physician decision, 15 had a high risk of bleeding, and 20 stopped for “other” reasons.
Twenty-three patients in this group were lost to follow-up.
Results
The researchers followed the patients for a year after they had finished treatment for their first VTE.
The risk of recurrent major VTE per 100 patient-years was:
- 3.0% among low-risk women who discontinued anticoagulants
- 8.1% among men and high-risk women who discontinued anticoagulants
- 7.4% among high-risk women (only) who discontinued anticoagulants
- 1.6% among men and high-risk women who continued anticoagulants.
Among the low-risk women who continued to receive anticoagulants, there were no cases of recurrent, symptomatic VTE.
“We see 2 to 3 patients with unexplained blood clots every day at The Ottawa Hospital,” Dr Rodger said. “If this rule was applied across Canada, we estimate that over 10,000 women a year would be identified as low risk and be able to come off blood thinners.”
