Real-world bleeding risk after DOAC initiation

Oral anticoagulation increases bleeding risk, especially following treatment initiation. In a non-clinical trial environment, it is not known if bleeding risk varies by time and indication with direct oral anticoagulants (DOAC) in patients with thrombosis.

At ISTH 2024, Jordan Schaefer (Rogel Cancer Center, Ann Arbor, Michigan, USA) presented the findings of a study that he conducted with his colleagues, which compared bleeding rates after DOAC initiation for non-valvular atrial fibrillation (AF) and venous thromboembolism (VTE).

How the study was conducted

Within the Michigan Anticoagulation Quality Improvement Initiative (MAQI²), the investigators analysed monthly bleeding rates for patients newly initiated on DOAC within four anticoagulation clinics. The team compared non-major bleeding, major bleeding, and all bleeding rates by indication for AF or VTE.

What were the results?

The study included 1,919 patients with AF and 744 with VTE. Most patients were using apixaban (54–82%) or rivaroxaban (17–46%).

Bleeding events for VTE

Patients with VTE had 109.7 versus 54.8 bleeding events per 100 patient–years in month 1 compared with month 2 (P=0.001). There was a significant decline in event rates over time (P<0.001). Major bleeding decreased significantly over time (P=0.008).

Bleeding events for AF

Patients with AF had 65.7 versus 43.1 bleeding events per 100 patient–years in month 1 compared with month 2 (P=0.008), with a significant decline in event rates over time (P<0.001). However, major bleed rates did not significantly change over time.

Patients with VTE had higher bleeding event rates than those with AF, with event rates highest the first month (109.7 versus 65.7 events per 100 patient–years for VTE and AF in month 1; P=0.001), then declining over time (26.8 versus 17.9 events per 100 patient–years for VTE and AF over months 1–12; P=0.045).

Clinical takeaways

• Bleeding rates were higher for VTE than AF in the initial 3 months of oral anticoagulation
• Duration of anticoagulant use should be considered when assessing studies on bleeding
• Clinicians should consider modifiable bleeding risk factors and follow up after initiating DOACs