The Figure shows the result of a retrospective medical review of data from primary care practices, looking at the intensity of anticoagulant therapy with warfarin in 660 patients with AFib who warranted oral anticoagulation therapy.  As shown in the Figure, 65% of the patients received no warfarin, and another 5% received warfarin but did not maintain the drug within the therapeutic range; out of the 660 patients, only 30% had warfarin serum levels that were at or above the therapeutic target level.  

Rothman SA. Am J Med 2013; 126: 00-00.