Significant number of patients being treated with aspirin in addition to direct oral anticoagulant without clear indication

1. Roughly 33.8% of patients with atrial fibrillation and/or venous thromboembolism undergoing treatment with a direct oral anticoagulant (DOAC) were also being treated with aspirin without a clear indication.

2. Patients being treated with DOAC and aspirin experienced significantly more bleeding events and hospitalizations, compared to DOAC monotherapy.

Evidence Rating Level: 2 (Good)

Study Rundown: The number of patients with atrial fibrillation (AF) or venous thromboembolism (VTE) taking acetylsalicylic acid (ASA) in combination with a direct oral anticoagulant (DOAC) is unclear. However, the frequency of this pharmacological combination is worth exploring to determine the risks associated with ASA use when combined with DOAC, and whether or not these risks are clinically warranted.

This registry-based cohort study of patients with AF or VTE, undergoing DOAC treatment, used data from four anticoagulation clinics in Michigan, U.S. between January 2015 and December 2019. Roughly 33% of patients were being treated with DOAC and ASA without a clear indication. This combination, compared to DOAC monotherapy, was associated with increased bleeding and hospitalizations.

Overall, this study found that, among patients with AF and/or VTE being treated with a DOAC, over one-third was also being treated with ASA without a clear indication. With increased rates of bleeding events and hospitalizations among the DOAC+ASA group, compared to DOAC monotherapy, it is important to recognize the risks associated with adding ASA among this patient population and weigh the potential benefits of straying from DOAC monotherapy.

Click to read the study in JAMA Internal Medicine

Relevant Reading: Comparative Effectiveness of Direct Oral Anticoagulants and Warfarin in Patients With Cancer and Atrial Fibrillation

In-Depth [ retrospective cohort]:

It is unclear the degree to which ASA (or aspirin) is prescribed in combination with a DOAC for patients with AF or VTE. Further, it is possible that the addition of ASA may increase bleeding and hospitalization risk among patients with AF and/or VTE. This registry-based cohort study investigated the frequency of this pharmacological combination and the outcomes associated with it, compared to DOAC monotherapy. Main outcomes were bleeding, emergency department visits, hospitalizations, rates of thrombosis, and death.

A total of 3,280 patients (M [SD] age = 68.2 [13.3] years, 49.0% female) were included from four clinics in Michigan, U.S. Approximately 33.8% of these patients, each with AF and/or VTE and no recent history of myocardial infarction or heart valve replacement, were being treated with DOACs and ASA without a clear indication for ASA.   Two propensity score-matched cohorts of 1,047 patients were further analyzed to determine differences in risks and outcomes among DOAC+ASA and DOAC monotherapy, with a mean (SD) follow-up of 20.9 (19.0) months. Patients in the DOAC+ASA group experienced significantly more bleeding events compared to the DOAC monotherapy group (difference 5.6 bleeds per 100 patient years, p = .01). Differences were primarily with nonmajor bleeding (difference 4.4 bleeds per 100 patient years, p = .02), with major bleeding rates being similar between groups. Patients taking DOAC+ASA were also more often hospitalized, compared to the DOAC monotherapy group (p = .02). However, rates of thrombotic events were similar between groups (p = .80).

Image: PD

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