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The risk of stroke rose steeply at INRs below 2.0.At an INR of 1.7,the adjusted odds ratio for stroke,as compared with the risk at an INR of 2.0, was 2.0(95 percent confidence interval,1.6 to 2.4);at an INR of 1.5,it was 3.3(95 percent confidence interval,2.4 to 4.6);and at an INR of 1.3,it was 6.0(95 percent confidence interval,3.6 to 9.8).Other independent risk factors were previous stroke(odds ratio,10.4;95 percent confidence interval,4.4 to 24.5),diabetes mellitus(odds ratio 2.9;95 percent confidence interval,1.3 to 6.5),hypertension(odds ratio,2.5;95 percent confidence interval,1.1 to 5.7),and current smoking(odds ratio,5.7;95 percent confidence interval,1.4 to 24.0).Among patients with atrial fibrillation,anticoagulant prophylaxis is effective at INRs of 2.0 or greater.Since previous studies have indicated that the risk of hemorrhage rises rapidly in INRs greater than 4.0 to 5.0,tight control of anticoagulant therapy to maintain the INR between 2.0 and 3.0 is a better strategy than targeting lower,less effective levels of anticoagulation. |
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