Newer blood thinners tied to less bleeding in sickle cell disease study
DOACs had similar clot recurrence, major bleeding rates as warfarin
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Newer oral anticoagulants, or blood thinners, were linked to a lower risk of clinically relevant nonmajor bleeding than warfarin, an older blood thinner, in adults with sickle cell disease (SCD) treated for dangerous blood clots, according to a study led by researchers in Saudi Arabia.
However, no significant differences were seen between the treatments in overall clinical outcomes or in the risk of developing additional blood clots.
The study, “Management of venous thrombosis in sickle cell disease: a comparative study on the use of DOACs and warfarin,” was published in Research and Practice in Thrombosis and Haemostasis.
Blood clots are a serious risk in SCD
SCD is a common inherited blood disorder in some parts of the world, including Saudi Arabia, where carrier rates can be especially high.
The disease is marked by abnormally shaped red blood cells that can block blood flow and deprive tissues of oxygen, a process that can lead to painful vaso-occlusive crises (VOCs). These blockages, along with other changes in the blood and blood vessels, also make people with SCD more likely to develop dangerous blood clots, known as venous thromboembolism (VTE). In fact, an estimated 11% of people with SCD will have a VTE before age 40, and recurrent clots are also common.
Blood thinners are used to treat and prevent these clots. For many years, vitamin K antagonists (VKAs) — including warfarin — were the standard oral anticoagulant therapy. These medicines work by blocking vitamin K, which the liver needs to make several blood-clotting proteins. This reduces the blood’s ability to form harmful clots.
However, VKAs can be difficult to manage because they require regular blood testing and can interact with foods and other medications.
Newer direct oral anticoagulants (DOACs) — such as rivaroxaban, dabigatran, edoxaban, and apixaban — are easier to use and have been linked in some studies to a lower risk of bleeding.
In this study, researchers in Saudi Arabia retrospectively analyzed data from 99 adults with SCD who developed a first VTE. Their mean age was 32.8 years, and 60.6% were women. The patients were followed between 2013 and 2023 at three hospitals in Saudi Arabia, Oman, and Kuwait.
A total of 67 patients (67.7%) were treated with a DOAC and 32 (32.3%) with warfarin. Among DOAC users, rivaroxaban was the most common (44 patients), followed by apixaban (21 patients) and dabigatran (two patients).
Before treatment, bleeding risk was similar between groups, but acute chest syndrome, a form of lung injury associated with SCD, was more frequent in the DOAC group.
DOACs linked to lower nonmajor bleeding risk
Pulmonary embolism — a blood clot that travels to and blocks blood vessels in the lungs — was the most common clot type, seen in 64 patients (64.6%). This was followed by proximal deep vein thrombosis, a clot that forms in the larger deep veins, usually of the legs or pelvis, in 23 patients (23.2%).
A little more than half of the patients (57.6%) were on hydroxyurea, a standard SCD treatment, at the time of VTE diagnosis.
Patients were followed for a median of 44 months, or a little more than 3.5 years, and the median duration of anticoagulant treatment was 12.5 months. About two-thirds of patients received parenteral anticoagulation, given by injection or infusion, before switching to an oral anticoagulant.
Nine patients (9.1%) developed another VTE. In three of them, this occurred within six months after the first event. Two of these patients were on rivaroxaban, and one was taking warfarin at the time of the recurrence.
Six patients developed additional clots more than one year after the first event. Two had discontinued anticoagulant therapy, two were on DOACs, and two were on warfarin.
Statistical analyses showed no significant differences between the warfarin and DOAC groups in the risk of developing another blood clot after the first episode.
Major bleeding risk did not differ significantly between the two groups. However, the risk of clinically relevant nonmajor bleeding was significantly lower in patients treated with DOACs.
Four patients died during the study period.
Overall, these findings suggest that DOACs are associated with a “relatively lower risk of bleeding than warfarin in the management of patients with SCD with venous thrombosis,” the researchers wrote. They added that appropriately controlled trials “are required to further confirm our findings.”
