According to an updated review in Thrombosis Research, the risk of major bleeding with vitamin K antagonists (VKA) was higher than with aspirin. These findings oppose data from previous meta-analysis and observational studies that suggested bleeding risks associated with VKA and aspirin were similar.

Researchers from the University of Ottawa and Argentina conducted a systematic review to determine the odds ratios (ORs) of major bleeding, intracranial bleeding or major extracranial bleeding of anticoagulation with VKA vs. low-dose aspirin. They included randomized controlled trials that reported bleeding rates in adults randomized to a VKA (INR 2–3) or to aspirin alone (<325mg per day). 

RELATED: Who Should Take Daily Aspirin? Uncertainty Still Remains

A total of 15 trials were included which reported data from 2,511 patients treated with VKA alone, and 2,471 patients treated with aspirin alone. They found that VKA use was tied to a higher risk of major bleeding (OR 1.76, 95% CI: 1.33–2.33) compared to aspirin. The odds ratio associated with VKA use for intrancranial bleeding was 1.74 (95% CI: 0.83–3.62) and 1.66 (95% CI: 0.94–2.92) for extrancranial bleeding. 

However, for trials obtaining good control of anticoagulation (time in therapeutic range [TTR] >65%), the bleeding risk with VKA was similar to that of aspirin (OR 1.16, 95% CI: 0.79–1.71), study authors noted.

For more information visit