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Author Notes:

Nita A. Limdi, Pharm.D, PhD, MSPH, Department of Neurology, University of Alabama at Birmingham, 1235 Jefferson Tower, 625 19th Street South, Birmingham AL 35294-0021, nlimdi@uab.edu, Phone: (205) 934-4385.

We are grateful to all the patients that participated in the study.

We thank our research nurses for their untiring efforts with patient recruitment, and the medical faculty and staff of the Anticoagulation Clinic for their help with identification of potential participants.

The authors report no conflict of interest.


Research Funding:

This work was supported in part by grants from the National Heart Lung and Blood Institute (RO1HL092173; 1K24HL133373), National Institute of General Medical Sciences (R01GM081488) and the National Institutes of Health (NIH) Clinical and Translational Science Award (CTSA) program (UL1TR000165).


  • Science & Technology
  • Life Sciences & Biomedicine
  • Biotechnology & Applied Microbiology
  • Genetics & Heredity
  • Pharmacology & Pharmacy
  • anticoagulation control
  • hemorrhage
  • percent time in target range
  • race
  • warfarin

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


Journal Title:

Pharmacogenetics and Genomics


Volume 27, Number 10


, Pages 347-355

Type of Work:

Article | Post-print: After Peer Review


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.

Copyright information:

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

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