Patients with atrial fibrillation or a history of VTE who take a daily aspirin in addition to a prescribed DOAC to treat or prevent blood clots had significantly higher rates of bleeding complications compared with those taking a DOAC alone, according to a new report from six anticoagulation clinics across the state of Michigan. Researchers also found no differences in stroke, heart attack, or blood clots between the groups after one year.

“The role of aspirin in combination with the newer DOACs is not well understood,” said lead study author Jordan Schaefer, MD, of the Division of Hematology/Oncology at the University of Michigan. “Based on our findings, adding aspirin may do more harm than good for some patients, increasing bleeding rates without improvements in the incidence of thrombosis.”

Of the 2,045 patients initially followed for the study, nearly one-third (647) were taking aspirin even though there was no clear indication to do so, such as a recent heart attack.

“We continue to see high numbers of patients taking aspirin, which is readily available over-the-counter, and that means clinicians may not know a patient is taking it,” Dr. Schaefer said. “There must be careful consideration of the relative risks and benefits of adding or continuing aspirin for patients on DOAC therapy.”

DOACs such as apixaban, dabigatran, edoxaban, and rivaroxaban are a newer group of blood thinners that are frequently prescribed to prevent stroke in people with atrial fibrillation, a common and serious heart rhythm disorder, and treat or guard against repeat episodes of deep vein thrombosis or pulmonary embolism. Records did not indicate whether aspirin therapy was initiated by the patient or recommended by a clinician.

Of the total number of patients, researchers focused their analysis on two groups of 639 matched patients that had similar demographics, co-morbidities, and concurrent medications. Of the patients taking aspirin, most (90.3%) were taking low dose aspirin (≤ 100 mg per day). Compared with patients taking a DOAC alone, those taking a DOAC plus aspirin had 319 versus 261 bleeding events, a 22% jump in bleeds, over an average follow-up of 15 months. This difference was largely driven by clinically relevant non-major bleeding events, which were nearly 40% higher with dual therapy. Bleeding sites were most commonly bruising, intestinal bleeding, or bleeding through the urinary tract. Observed rates of thrombosis (stroke, VTE, and heart attacks) were similar between patients taking both medicines and those only on a DOAC (19 and 18 events). The only two fatal bleeding events were seen among patients on DOACs only. Patients on combination therapy had more emergency room visits and hospitalizations mostly due to bleeding, but these differences did not reach statistical significance.

“For patients prescribed a DOAC, whether to add or continue aspirin is a common clinical question. For some patients, we didn’t see a clear benefit,” Dr. Schaefer said. “It’s really important for clinicians to assess whether patients are using aspirin and, equally, it’s important that patients not simply take a medicine because it’s easy to get over-the-counter, but rather talk with their doctor about whether it’s safe and whether there is an important need for it.”

He said he hopes these data will raise awareness within the medical community and lead to interventions aimed at reducing the number of patients inappropriately on aspirin perhaps by instituting electronic medical record alerts or leveraging local anticoagulation experts.

The current study further bolsters earlier research by Dr. Schaefer and his team published in JAMA Internal Medicine that found that some patients using aspirin and warfarin, a different type of anticoagulant, experienced a higher rate of bleeding events compared with those taking warfarin alone. Similar to the current study, there were no observed difference in rates of heart attack, stroke, or VTE. Further study is needed to determine whether DOACs plus aspirin is safer than warfarin plus aspirin and to be able to compare bleeding events and the outcomes of the individual DOACs.

Although the study is limited to Michigan, researchers said the mix of clinics were representative of different patients, geographic regions (urban, suburban, and rural), and academic and community centers. Because of the small size of the study, the researchers caution that they were not able to fully assess for differences in clotting outcomes or evaluate some important subgroups, including those that might benefit from adding aspirin.

This article is a news release from American Society of Hematology Annual Press Meeting. Read the original here.