Patient characteristics associated with oral anticoagulation control: results of the Veterans AffaiRs Study to Improve Anticoagulation (VARIA)

J Thromb Haemost. 2010 Oct;8(10):2182-91. doi: 10.1111/j.1538-7836.2010.03996.x.


Background: In patients receiving oral anticoagulation, improved control can reduce adverse outcomes such as stroke and major hemorrhage. However, little is known about patient-level predictors of anticoagulation control.

Objectives: To identify patient-level predictors of oral anticoagulation control in the outpatient setting.

Patients/methods: We studied 124,619 patients who received oral anticoagulation from the Veterans Health Administration from October 2006 to September 2008. The outcome was anticoagulation control, summarized using percentage of time in therapeutic International Normalized Ratio range (TTR). Data were divided into inception (first 6 months of therapy; 39,447 patients) and experienced (any time thereafter; 104,505 patients). Patient-level predictors of TTR were examined by multivariable regression.

Results: Mean TTRs were 48% for inception management and 61% for experienced management. During inception, important predictors of TTR included hospitalizations (the expected TTR was 7.3% lower for those with two or more hospitalizations than for the non-hospitalized), receipt of more medications (16 or more medications predicted a 4.3% lower than for patients with 0-7 medications), alcohol abuse (-4.6%), cancer (-3.1%), and bipolar disorder (-2.9%). During the experienced period, important predictors of TTR included hospitalizations (four or more hospitalizations predicted 9.4% lower TTR), more medications (16 or more medications predicted 5.1% lower TTR), alcohol abuse (-5.4%), female sex (- 2.9%), cancer (-2.7%), dementia (-2.6%), non-alcohol substance abuse (-2.4%), and chronic liver disease (-2.3%).

Conclusions: Some patients receiving oral anticoagulation therapy are more challenging to maintain within the therapeutic range than others. Our findings can be used to identify patients who require closer attention or innovative management strategies to maximize benefit and minimize harm from oral anticoagulation therapy.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Administration, Oral
  • Adult
  • Aged
  • Anticoagulants / administration & dosage
  • Anticoagulants / therapeutic use*
  • Atrial Fibrillation / drug therapy
  • Cardiology / methods
  • Female
  • Humans
  • International Normalized Ratio
  • Male
  • Middle Aged
  • Regression Analysis
  • United States
  • United States Department of Veterans Affairs
  • Veterans
  • Warfarin / therapeutic use


  • Anticoagulants
  • Warfarin