ABC-Bleeding Score Stratifies Risk in A-fib Patients on OAC and Aspirin

The ABC (age, biomarkers, and clinical history)-bleeding risk score can differentiate major bleeding risk in patients taking both an oral anticoagulant and aspirin, a post hoc analysis of data from the ARISTOTLE and RE-LY trials shows.

When patients had a low estimated risk of major bleeding based on the score, adding aspirin on top of anticoagulation was not associated with a large jump in observed bleeding. On the other hand, when patients had a high estimated risk, concomitant aspirin use was associated with a substantially greater hazard of major bleeding.

“Previously, it has been very challenging to accurately assess bleeding risk in patients with atrial fibrillation, and even more so if the patients are on concomitant aspirin in addition to an oral anticoagulant. There is now robust scientific data in support of the clinical usefulness of the ABC-bleeding risk score in this setting,” lead author Ziad Hijazi, MD, PhD (Uppsala University, Sweden), told TCTMD in an email.

“From a clinical viewpoint, the results show that the ABC-bleeding risk score may be a useful tool for decision support concerning intensity and duration of combination antithrombotic treatment in patients with atrial fibrillation and coronary artery disease,” he continued. “So, the use of the ABC-bleeding risk score, either routinely or in specific cases, provides clinicians and patients with atrial fibrillation better understanding of the general risk of major bleeding as well as the specific risk conferred by potential use of concomitant antiplatelet therapy.”

But not everyone is convinced the score is ready for widespread clinical use for this purpose. Geoffrey Barnes, MD (University of Michigan, Ann Arbor), noted that there are randomized trials calling into question whether aspirin is needed at all in this setting, that the biomarkers included in the ABC score are not typically measured in this population, and that there are no prospective studies evaluating the impact of applying this tool on treatment decision-making and patient outcomes.

The study is “interesting, thought-provoking, and hypothesis-generating, but I’m not sure [the score is] ready for prime time just yet,” Barnes commented.

A Clinical Challenge

Many patients with A-fib also have coronary disease, meaning that they could have indications for both oral anticoagulation to prevent stroke and antiplatelet therapy to prevent MI and stent thrombosis. Physicians have long faced the conundrum of how to best balance the bleeding risks and the ischemic benefits when using multiple antithrombotic therapies.

Risk scores may help in decision-making. The ABC-bleeding risk score was developed recently to assess major bleeding risk in patients with A-fib who are taking an oral anticoagulant, and it has been mentioned in European guidance on A-fib and dual antiplatelet therapy.

“The biomarker-based ABC risk scores provide more-accurate risk prediction in patients with atrial fibrillation than traditional risk scores such as the CHA₂DS₂-VASc and HAS-BLED scores for stroke and bleeding risk, respectively,” Hijazi said. “However, there are certain clinical settings that introduce additional challenges in the risk assessment. Such a setting is patients that have coronary heart disease in addition to atrial fibrillation.”

It was striking that the clinically based HAS-BLED score did not discriminate properly regarding the increased risk of bleeding in patients on concomitant aspirin therapy. Ziad Hijazi

The investigators tackled how the ABC-bleeding risk score performed in those types of patients in the current study, which was published online recently in JAMA Network Open. They used data on 24,349 total patients from the ARISTOTLE and RE-LY trials, which pitted the direct oral anticoagulants apixaban (Eliquis; Bristol-Myers Squibb) and dabigatran(Pradaxa; Boehringer Ingelheim), respectively, against warfarinin patients with A-fib. Some patients in each trial received concomitant aspirin—in RE-LY, 36.4% of patients took aspirin at some point during follow-up, and in ARISTOTLE, 31.0% of patients were on aspirin on day 1 and about 20% were taking it at any time after that.

ISTH major bleeding occurred at a higher rate during follow-up in patients taking aspirin on top of their oral anticoagulation than in those on anticoagulation alone in both ARISTOTLE (4.04% vs 2.24%) and RE-LY (4.18% vs 2.14%).

For patients with the lowest estimated major bleeding risk based on the ABC score—less than 1.1% and 1.3% annually in the ARISTOTLE and RE-LY trials, respectively—the observed rates remained low even when aspirin was added on. However, for patients at the highest estimated risk—greater than 2.5% and 2.8% annually in the respective trials—concomitant aspirin was associated with significantly higher rates of major bleeding in both ARISTOTLE (HR 1.65; 95% CI 1.40-1.95) and RE-LY (HR 1.70; 95% CI 1.42-2.04).

The investigators then compared the ABC-bleeding risk score with another major assessment tool—HAS-BLED—based on clinical variables alone. “It was striking that the clinically based HAS-BLED score did not discriminate properly regarding the increased risk of bleeding in patients on concomitant aspirin therapy,” Hijazi said.

Questions Remain

In an accompanying editorial, Celina Yong, MD, MBA (Stanford University School of Medicine and VA Palo Alto Health Care System, CA), and John Bittl, MD (AdventHealth Ocala, FL), ponder how the ABC score would fit into clinical practice.

“We propose that the ABC-bleeding risk score performs best in cases when bleeding risk is low but there is concern about continuing aspirin,” they write. “When faced with a patient who needs anticoagulation for atrial fibrillation and also has a preexisting indication for aspirin, a clinician may be reassured by a low ABC-bleeding risk score to safely continue dual antithrombotic therapy with aspirin and an anticoagulant, at least for 2 years.”

But like Barnes, Yong and Bittl identified some limitations of the study, including the fact that aspirin use was not part of the randomization in the trials and that it remains unknown how the ABC score would work outside of the stable CAD population.“For patients in whom indications for aspirin may be stronger than for those enrolled in the present study,” they say, “the clinician must still face the question, ‘What is the risk of stopping aspirin in patients at high risk for ischemic events?’”

Moreover, the editorialists and Barnes both point out that using the ABC-bleeding risk score entails extra resources to obtain information on biomarkers that are not routinely collected for patients with A-fib and stable CAD—namely, high-sensitivity troponin and growth differentiation factor 15 (GDF-15). “It would be a big change in the way we currently practice,” Barnes said.

Hijazi pushed back on the idea that the need to obtain information on biomarkers represents an obstacle to wider use of the score. “With the widespread use of electronic healthcare records, smartphones, mobile data, big data, etc, the pendulum has undoubtedly tilted to the preference of more-accurate risk assessment as opposed to ‘keep it simple’ clinical scores at the expense of accuracy,” he said. “Sometimes blood sampling is suggested as a potential barrier, but I respectfully disagree, since most clinicians already routinely draw blood samples in order to check hemoglobin and kidney and liver function before starting treatment with oral anticoagulants or during routine checkups.”

Barnes and the editorialists see a need for additional research. Yong and Bittl call for independent validation of the ABC-bleeding risk score in a similar cohort and a prospective investigation in patients with recent acute coronary syndromes. Barnes said he wants to see a prospective study randomizing patients to concomitant aspirin or anticoagulation alone based on the ABC score.

The current retrospective study is “potentially helping us move the needle, but before [the score] goes into widespread practice,I think we really need some of that prospective data to define exactly how it’s going to impact care decisions,” Barnes said.

Hijazi et al note in their paper that the score is being prospectively evaluated in the ongoing ABC-AF study. The trial, with an estimated enrollment of 6,500, will randomize patients to therapy guided by the risk score or to standard care.