title: Pathways to poor anticoagulation control.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Center for Healthcare Organization and Implementation Research, Bedford VA Medical Center, Bedford, MA, USA; Department of Medicine, Section of General Internal Medicine, Boston University School of Medicine, Boston, MA, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Razouki
authors.forename: A
authors.initials: A
authors.lastname: Ozonoff
authors.forename: S
authors.initials: S
authors.lastname: Zhao
authors.forename: A J
authors.initials: AJ
authors.lastname: Rose
mesh_terms: D000328:Adult; D000368:Aged; D000437:Alcoholism / Q000150:complications; D000925:Anticoagulants / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000150:complications / Q000188:drug therapy*; D001714:Bipolar Disorder / Q000150:complications; D001777:Blood Coagulation / Q000187:drug effects; D003704:Dementia / Q000150:complications; D005260:Female; D006760:Hospitalization; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009369:Neoplasms / Q000150:complications; D019966:Substance-Related Disorders / Q000150:complications; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States; D014493:United States Department of Veterans Affairs; D054556:Venous Thromboembolism / Q000150:complications / Q000188:drug therapy*; D014859:Warfarin / Q000627:therapeutic use*; D055815:Young Adult
chemical_list: D000925:Anticoagulants; D014859:Warfarin
keywords: anticoagulants; international normalized ratio; quality of healthcare; veterans; warfarin