A bleeding-risk tool is needed that can determine which patients on oral anticoagulation therapy (OAT) for venous thromboembolism (VTE) may have an annual rate of major bleeding over 3%. “[Three percent] is the cut-point at which the risk of continued anticoagulant therapy exceeds the benefit,” said Philip S. Wells, MD, Department of Medicine, University of Ottawa and the Ottawa Hospital in Ontario, Canada. Wells presented the research at the 58th American Society of Hematology Annual Meeting and Exposition in San Diego, CA.  

The current tools focus on a higher bleeding-risk period of the first three months of OAT therapy (risk of major bleeding 2.4% in the first three months vs. 2% per year thereafter), but they do not evaluate for bleeding risk after the first three months of therapy (extended OAT).

The study authors sought to determine wheter the rates of major bleeding had exceeded 3% at the time that four other existing, previously published tools classified VTE patients during extended OAT as being at high risk for major bleeding. They also evaluated whether the differences in major bleeding risk between high-risk and not-high risk patients were statistically significantly dissimilar. 

The researchers generated a new prediction model, created from a 12-site, multinational prospective cohort study of 2,514 patients on extended OAT for unprovoked VTE, or provoked VTE with prior VTE. Patients were enrolled after at least three months of OAT. Participants had a mean age of 60.2 years, and more were male (64%) and Caucasian (92%). 

All major bleeding events during long-term OAT—a mean period of 2.8 years—were captured and adjudicated. The authors then applied the four previously published tools to analyze the risk for major bleeding per patient scores; the study didn’t include all variables from the tools, including drug and alcohol history. In all, 121 patients experienced at least one episode of major bleeding. The annual rate of bleeding was 1.7 per 100 patient years of observation. 

The researchers found that the proportion of patients classified at high risk for major bleeding by the four previously published tools were greater than 3%, showing that “despite the potential to underestimate risk due to missing variables, all currently available prediction tools are able to identify patients with a 3% or higher risk of major bleeding per year,” said Wells.