This study was stopped early because patients who received Xarelto® had more new blood clots than patients who received warfarin.
Note: Not all patients with APLAS are triple-positive, and the results of taking Xarelto® in patients who are only positive for 1 or 2 antiphospholipid antibody types are unknown
Understanding the problem
Antiphospholipid antibodies are abnormal proteins produced by the immune system that mistakenly attack proteins that are attached to fats called "phospholipids" found within the lining of blood cells and blood vessels. These antibodies can increase a person's risk of developing a blood clot within arteries and veins and can cause women to have difficulty having successful pregnancies. APLAS is rare and testing for the antibodies should only be done when doctors have a strong suspicion of APLAS and if knowledge of the test result will change how the patient is managed (i.e. should not be routinely done after a DVT or PE).
There are three different types of antiphospholipid antibodies that can be detected using blood tests. People who have positive tests for all three types of antibodies are called "triple-positive". They have the highest risk of developing blood clots in their arteries and veins as well as the highest risk of having new blood clots despite taking anticoagulants.
People who take warfarin (an anticoagulant) need to have regular blood measurements, called an INR, to ensure the medication dose is correct. Warfarin may interact with food and lots of other medications. For these reasons, some people dislike taking warfarin. Xarelto® is an anticoagulant pill that does not require blood testing and interacts with very few medications, which is why some people prefer to take it instead of warfarin.
The question asked by researchers for this study was, “Is it safe and effective for patients with triple-positive APLAS who have a history of blood clots to take Xarelto® instead of warfarin to prevent new blood clots?”
Who? The study included 120 people aged 18-75 years (average 46 years; 64% female) who had triple-positive APLAS and a history of a blood clot in a vein or artery.
What? The study measured the rates of new blood clots, major bleeding, and death due to blood clots in patients who received Xarelto® compared with patients who received warfarin.
Xarelto® 20 mg once a day
Xarelto® 15 mg once a day, in patients with kidney disease
Warfarin adjusted to maintain a target INR between 2 and 3
Xarelto® compared with warfarin in patients with triple positive APLAS
Rate of events with Xarelto®
Rate of events with warfarin
Arterial blood clot (stroke or heart attack)
12 out of 100 people
0 out of 100 people
About 12 more people out of 100 had an arterial blood clot while taking Xarelto®
Venous blood clot (DVT or PE)
0 out of 100 people
0 out of 100 people
|Major bleeding||7 out of 100 people||3 out of 100 people|
|Death||0 out of 100 people||0 out of 100 people||No difference|
*Although the rates for the 2 groups look different, the differences were not statistically significant—this means that the difference could be due to chance or to the small number of patients studied rather than due to the different treatments.
This Evidence Summary is based on the following article:
Pengo V, Denas G, Zoppellaro G, et al. Rivaroxaban vs warfarin in high-risk patients with antiphospholipid syndrome. Blood. 2018 Sep 27;132(13):1365-1371. doi: 10.1182/blood-2018-04-848333. Epub 2018 Jul 12. PubMed
Carolyne Elbaz, MDCM
Carolyne is currently enrolled in the Alexandra Yeo Hemostasis and Thrombosis fellowship at the University of Toronto. She completed her medical school and Internal Medicine residency at McGill University and Hematology fellowship at the Université de Montréal. She plans to complete a Masters in Health Professional and Teachers Education to launch a career in Medical Education. She is interested in hemostasis and coagulation research as well as educational tools for health professionals.
Bill Geerts, MD, FRCPC
Dr. Bill Geerts is Professor of Medicine at the University of Toronto and a Thromboembolism consultant at Sunnybrook Health Sciences Centre. He is an active member of Thrombosis Canada.
Published: Friday, March 8, 2019
Last Updated: Thursday, July 30, 2020