Only a minority of patients with atrial fibrillation or venous thromboembolism achieved good anticoagulation control while on warfarin, according to a population-based data analysis by Ana Filipa Macedo and her colleagues at Boehringer Ingelheim in the United Kingdom. In fact, only 44% of 140,078 AF patients and 36% of 70,371 VTE patients assessed had an optimal International Normalized Ratio (INR) time in therapeutic range (TTR) more than 70% of the time while on warfarin.
Patient characteristics associated with a significant increase in time spent above or below the recommended INR range of 2.0-3.0 were current smoking, the use of NSAIDs, age less than 45 years, and a body mass index less than 18.5 kg/m2 in both AF and VTE patients, whereas patients with VTE alone had predictors of poor control that included chronic obstructive pulmonary disease or asthma, heart failure, and active cancer.
“The study provides evidence that in the first 12 months of warfarin use, there is a high amount of unpredictable variability in an individual’s TTR,” the researchers summarized. “These findings confirm the difficulty of achieving high-quality anticoagulation with warfarin in real-world clinical practice and can be used to identify patients who require closer monitoring or innovative management strategies,” the authors added.
More of the study can be read here (Thromb Res. 2015 Aug; 136(2):250-260.).
The study received funding from Boehringer Ingelheim, and the authors disclosed that they were all employees of the company, which makes a variety of cardiovascular therapies, including anticoagulants.