Pathways to poor anticoagulation control

Authors

  • Z. Razouki,

    Corresponding author
    1. Center for Healthcare Organization and Implementation Research, Bedford VA Medical Center, Bedford, MA, USA
    2. Department of Medicine, Section of General Internal Medicine, Boston University School of Medicine, Boston, MA, USA
    • Correspondence: Zayd Razouki, Center for Healthcare Organization and Implementation Research, Bedford VA Medical Center, Bedford, MA and Department of Medicine, Section of General Internal Medicine, Boston University School of Medicine, 801 Massachusetts Avenue, 2nd floor Boston, Boston, MA 02118, USA.

      Tel.: +1 617 414 6663; fax: +1 617 414 4676.

      E-mail: zrazouki@bu.edu

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  • A. Ozonoff,

    1. Center for Healthcare Organization and Implementation Research, Bedford VA Medical Center, Bedford, MA, USA
    2. Biostatistics Section, Boston Children's Hospital, Boston, MA, USA
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  • S. Zhao,

    1. Center for Healthcare Organization and Implementation Research, Bedford VA Medical Center, Bedford, MA, USA
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  • A. J. Rose

    1. Center for Healthcare Organization and Implementation Research, Bedford VA Medical Center, Bedford, MA, USA
    2. Department of Medicine, Section of General Internal Medicine, Boston University School of Medicine, Boston, MA, USA
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  • Manuscript handled by: F. R. Rosendaal
  • Final decision: F. R. Rosendaal, 12 February 2014

Summary

Background

While a considerable amount is known about which patient-level factors predict poor anticoagulation control with warfarin, measured by percent time in therapeutic range (TTR), less is known about predictors of time above or below target.

Objective

To identify predictors of different patterns of international normalized ratio (INR) values that account for poor control, including ‘erratic’ patterns, where more time is spent both above and below INR target, and unidirectional patterns, where time out of range is predominantly in one direction (low or high).

Methods

We studied 103 897 patients receiving warfarin with a target INR of 2–3 from 100 Veterans Health Administration sites between October 2006 and September 2008. Our outcomes were percent time above and below the target range. Predictors included patients' demographics, comorbidities, and other clinical data.

Results

Predictors of erratic patterns included alcohol abuse (5.2% more time below and 3.7% more time above, P < 0.001 for all results), taking > 16 medications (4.6% more time below and 1.8% more time above compared to taking seven or fewer medications), and four or more hospitalizations during the study (6.6% more time below and 2% more time above compared to no hospitalization). In contrast, predictors like cancer, non-alcohol drug abuse, dementia, and bipolar disorder were associated with more time below the target range (3.4%, 5.2%, 2.6%, and 3.2%, respectively) and less (or similar) time above range.

Conclusion

Different patient-level factors predicted unidirectional below-target and ‘erratic’ patterns of INR control. Distinct interventions are necessary to address these two separate pathways to poor anticoagulation.

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