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Quality of anticoagulation control and hemorrhage risk among African American and European American warfarin users

Limdi, Nita A.a; Brown, Todd M.b; Shendre, Aditic; Liu, Nianjunc; Hill, Charles E.e; Beasley, Timothy M.d

doi: 10.1097/FPC.0000000000000298

Objective We evaluated whether percent time in target range (PTTR), risk of over-anticoagulation [international normalized ratio (INR)>4], and risk of hemorrhage differ by race. As PTTR is a strong predictor of hemorrhage risk, we also determined the influence of PTTR on the risk of hemorrhage by race.

Participants and methods Among 1326 warfarin users, PTTR was calculated as the percentage of interpolated INR values within the target range of 2.0–3.0. PTTR was also categorized as poor (PTTR<60%), good (60≤PTTR<70%), or excellent (PTTR≥70%) anticoagulation control. Over-anticoagulation was defined as INR more than 4 and major hemorrhages included serious, life-threatening, and fatal bleeding episodes. Logistic regression and survival analyses were carried out to evaluate the association of race with PTTR (≥60 vs. <60) and major hemorrhages, respectively.

Results Compared with African Americans, European Americans had higher PTTR (57.6 vs. 49.1%; P<0.0001) and were more likely to attain 60≤PTTR<70% (22.9 vs. 13.1%; P<0.001) or PTTR of at least 70% (26.9 vs. 18.2%; P=0.001). Older (>65 years) patients without venous thromboembolism indication and chronic kidney disease were more likely to attain PTTR of at least 60%. After accounting for clinical and genetic factors, and PTTR, African Americans had a higher risk of hemorrhage [hazard ratio (HR)=1.58; 95% confidence interval (CI): 1.04–2.41; P=0.034]. Patients with 60≤PTTR<70% (HR=0.62; 95% CI: 0.38–1.02; P=0.058) and PTTR of at least 70% (HR=0.27; 95% CI: 0.15–0.49; P<0.001) had a lower risk of hemorrhage compared with those with PTTR less than 60%.

Conclusion Despite the provision of warfarin management through anticoagulation clinics, African Americans achieve a lower overall PTTR and have a significantly higher risk of hemorrhage. Personalized medicine interventions tailored to African American warfarin users need to be developed.

aDepartment of Neurology

bDepartment of Medicine, Division of Cardiovascular Diseases

cDepartment of Epidemiology

dDepartment of Biostatistics, University of Alabama at Birmingham, Birmingham, Alabama, USA

eDepartment of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia, USA

Present address: Aditi Shendre: Richard M. Fairbanks School of Public Health, Indianapolis University–Purdue University Indianapolis, Indianapolis, Indiana, USA.

Correspondence to Nita A. Limdi, PharmD, PhD, MSPH, Department of Neurology, University of Alabama at Birmingham, 1235 Jefferson Tower, 625, 19th Street South, Birmingham, AL 35294-0021, USA Tel: +1 205 934 4385; fax: +1 205 996 9912; e-mail:

Received March 7, 2017

Accepted June 29, 2017

Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.