Net Clinical Benefit of Warfarin

Abstract

The decision to use antithrombotics for stroke prevention in atrial fibrillation (AF) requires the assessment of an individual patient's risk of stroke balanced with their likelihood of bleeding on treatment. US practice guidelines have recommended the use of the CHADS2 score (Congestive heart failure, Hypertension, Age ≥75 years, Diabetes mellitus, Stroke [2 points]; graded from 0–6 according to presence of major risk factors; see the Table) for the assessment of stroke risk in patients with AF.1 However, this score cannot precisely categorize all patients at different risks of thromboembolism.2 The CHADS2 model does not account for certain previously underappreciated risk factors, including the increase in stroke risk with age in patients <75 years old and in those with vascular disease, and thus allocates many patients to the low- and intermediate-risk categories who might actually be relatively stroke prone.3 The 2010 European Society of Cardiology guidelines for the management of AF4 recommend use of the more inclusive CHA2DS2-VASc score (Congestive heart failure, Hypertension, Age ≥75 years [2 points], Diabetes mellitus, Stroke/TIA/Thromboembolism [2 points], Vascular disease, Age 65–74 years, Sex category; graded 0–9; see the Table), which incorporates additional risk factors, including age of 65 to 74 years and vascular disease. Validation studies have shown that the CHA2DS2-VASc score performs better than CHADS2 in distinguishing patients at low or intermediate thromboembolic risk.5 In a large Danish registry, thromboembolism rates at 1 year for patients at low risk (score=0) were 0.78%/y with CHA2DS2-VASc and 1.67%/y with CHADS2.6 View this table: Table. CHADS2, CHA2DS2-VASc, and HAS-BLED Risk Factors and Scoring Schema Article see p 2298 Risk models have also been developed to stratify bleeding risk in anticoagulated patients. The …