P849
Relationship between time in therapeutic range and study-level factors in patients treated with vitamin k antagonists: a systematic review and meta-regression Free

Background: Vitamin K antagonists (VKAs) are still widely used worldwide in patients with atrial fibrillation (AF) and venous thromboembolism (VTE). The safety and efficacy of VKAs are optimized only if the quality of anticoagulation is optimal. Several factors can affect quality of VKA treatment. We determined study-level factors and clinical setting effects on anticoagulation control in patients receiving VKAs.

Methods: We searched MEDLINE, CENTRAL and EMBASE for all published studies on patients receiving VKAs with a 2.0-3.0 target international normalized ratio (INR), reporting time in therapeutic range (TTR) calculated by Rosendaal’s linear interpolation.

Results: A total of 101 studies were included, with 128 VKA-treated study arms including 246,848 patients. Mean TTR was 62.2% (95% CI: 60.1 to 64.2%). Of the 128 studies included, 32 (25.0%) were randomized controlled trials (RCTs), 42 (32.8%) conducted in anticoagulation clinics and 54 (42.2%) in a community care setting. Meta-regression analysis found that patients treated in the community setting had the worst TTR compared to the setting of anticoagulation clinics (p<0.001) and RCTs (p=0.008). VKA-naïve patients had lower TTR than those VKA-experienced (p=0.006) and patients with mixed or unknown VKA-experience (p=0.008). Patients treated in Europe/UK showed a higher TTR than those treated in other geographical regions. Studies reporting on mixed indications, achieved a better TTR than studies based on AF only (p=0.037), with no difference was found between AF and VTE studies (p=0.856). Similar results were found on various AF subgroup analysis.

Conclusions: Several factors affect TTR in VKA-treated patients. Being managed by experienced physicians, RCT setting, prior VKA treatment or being treated in Europe conferred a greater likelihood of anticoagulation control.