title: International normalized ratio stabilization in newly initiated warfarin patients with nonvalvular atrial fibrillation.
abstract: BACKGROUND
  Warfarin is effective for stroke prevention in patients with atrial fibrillation (AF), but international normalized ratio (INR) levels fluctuate and frequent monitoring is necessary.
  
  
  METHODS
  This study used data from a large anticoagulation management service database to analyze the relationship between INR stabilization and warfarin utilization for >1 year in patients with nonvalvular AF (NVAF). Anticoagulation records from a large US electronic database collected from 2006 to 2010 were analyzed.
  
  
  RESULTS
  Patients with NVAF and ≥ 3 INR values in the dataset were identified (n = 15,276). INR stabilization was defined as the first three consecutive INR values between 2.0 and 3.0 after warfarin initiation. One quarter of patients (n = 3809) failed to reach INR stabilization. After initial stabilization, 30% of subsequent INR values were out of range. The mean (± standard deviation [SD]) follow-up time from stabilization to the end of study for these patients was 494.2 ± 418.1 days. Age ≥ 75 years (odds ratio [OR] = 1.17, 95% confidence interval [CI] = 1.08-1.27), hypertension (OR = 1.19, 95% CI = 1.10-1.29), or prior stroke (OR = 1.29, 95% CI = 1.04-1.61) were positively associated with achieving stabilization; heart failure was negatively associated with stabilization (OR = 0.78, 95% CI = 0.70-0.87). Male gender (p < 0.0001) and hypertension were associated with earlier stabilization (p = 0.0013); heart failure was associated with later stabilization (p = 0.0098). Patients who achieved INR stabilization within 1 year were 10 times more likely to remain on warfarin than patients who did not achieve it.
  
  
  CONCLUSIONS
  Observational data may contain incomplete records. Data on adherence, concurrent medications, vitamin K intake, genotype, reasons for discontinuation of monitoring, and patient outcomes were not available in the dataset. The study findings were generalizable only to patients with AF who were managed by anticoagulation clinics.
  
  
  CONCLUSIONS
  Given the importance of stroke prevention among patients with AF, the potential for unpredictable INR patterns should be carefully considered during clinical decision-making.
authors.affiliation: Janssen Scientific Affairs LLC , Raritan, NJ , USA.
authors.forename: Winnie W
authors.initials: WW
authors.lastname: Nelson
authors.forename: Sunita
authors.initials: S
authors.lastname: Desai
authors.forename: C V
authors.initials: CV
authors.lastname: Damaraju
authors.forename: Lang
authors.initials: L
authors.lastname: Lu
authors.forename: Larry E
authors.initials: LE
authors.lastname: Fields
authors.forename: Peter
authors.initials: P
authors.lastname: Wildgoose
authors.forename: Jeff R
authors.initials: JR
authors.lastname: Schein
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000097:blood* / Q000150:complications*; D016208:Databases, Factual; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D020521:Stroke / Q000209:etiology / Q000517:prevention & control*; D016896:Treatment Outcome; D014481:United States; D014859:Warfarin / Q000627:therapeutic use*; D055815:Young Adult
chemical_list: D000925:Anticoagulants; D014859:Warfarin
keywords: International normalized ratio; Nonvalvular atrial fibrillation; Stabilization; Warfarin