A decision-making algorithm appears to give patients and clinicians a way to safely end anticoagulation therapy in a group of women who develop so-called unprovoked deep vein thrombosis, researchers reported here.
Of the women who discontinued blood thinners based on the so-called HERDOO2 rule, three recurrent venous thromboembolism events were recorded per 100 patient-years, reported Marc Rodger, MD, chief and chair of hematology at the University of Ottawa.
In his presentation at the annual European Society of Cardiology congress, Rodger said that compared well with the finding in the same study that patients who remained on anticoagulation experienced 1.6 events per 100 patient years. Although the rate was higher, Rodger told MedPage Today that the difference was offset by the 1%-1.5% of patients on blood thinners who may develop major bleeding events that can be life-threatening.
“We found that women with 0-1 HERDOO points had low risk of recurrences, and could stop blood thinners and they did well,” he said. “It is a very difficult decision to consider whether to continue blood thinners life-long or not. So to have a simple tool that you can apply after short term therapy to identify a low-risk group makes it that much more comfortable for everybody.”
The HERDOO2 rule consists of four features:
- HER — hyperpigmentation, edema, or redness in either leg
- D – level of D-dimer assessed through blood testing
- O – Obesity defined as body mass index of 30 or greater
- O – Older than 65 years of age
A score of 0-1 puts one at low risk; a score of 2-4 is considered high risk.
“I’m sorry, fellows,” Rodger said, “The rule only applies to women.” He said attempts to tease out factors that differentiate in men failed, possibly due to the role testosterone plays in males.
“We have previously devised a clinical rule or scoring system to identify low risk patients who could stop anticoagulation after blood clots that come out of the blue or unprovoked blood clots,” Rodger said. “With a derivation study it is just a hypothesis. You need to validate it before clinicians can use it in prime time.”
“This was a validation study in 2,779 patients worldwide and we showed that the HERDOO2 rule can identify low-risk women that can stop blood thinners after short term anticoagulation use,” he said.
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In the study, 631 women were deemed to be low risk and 591 of them discontinued blood thinners with 3.0 per 100 patient years developing recurrent clots. The other low-risk women opted to stay on blood thinners, and none of them developed clots during the 12-month follow-up.
Of the 2,148 persons who were found to be at high risk, 1,802 remained on blood thinners and their rate of recurrent venous thromboembolism (VTE) was 1.6 per 100 person-years; of the 323 patients who opted not to go on anticoagulation in this high-risk group, 8.1 events occurred per 100 patient years, Rodger reported.
Rodger said that the low rates of recurrence among people taking blood thinners attest to the effectiveness of the agents in preventing VTE recurrences. He said that it is estimated that if untreated, about half the patients who experience VTE will have a recurrence in their lifetime.
In commenting on the study, Alfred Bove, MD, PhD, past president of the American College of Cardiology, and professor emeritus of medicine at Temple University, Philadelphia, told MedPage Today, “The REVERSE II study asks the question of whether we can stop anticoagulation in people with deep vein thrombosis, and we don’t have good criteria for that. Right now if you look at the guidelines, some of them say lifetime anticoagulation after a single episode, others say 6 months and other will say a year.
“The basic issue here is that venous thrombosis is a common problem. Getting a spontaneous phlebitis in your leg puts the patient at risk for pulmonary embolism. If we could discriminate that group of patients that can be low risk subsequent to an event we could make some important clinical decisions. This study gives us some way to discriminate the lower risk from the higher risk patients,” Bove said.