title: How well does the target INR level maintain in warfarin-treated patients with non-valvular atrial fibrillation?
abstract: OBJECTIVE
  Although warfarin is an effective oral anticoagulation (OAC) drug to reduce the risk of thromboembolism in patients with non-valvular atrial fibrillation (NVAF), long term follow-up data are scarce to be certain whether the target INR level is maintained in warfarin-treated patients in Korea. The aim of this study was to evaluate how well INRs are maintained within the target range using a new index, INR stability (= 100 x number of INRs within target range/total number of INR measurements) which we made, and to find out any correlation between thromboembolic events and INR stability.
  
  
  METHODS
  This study was an observational analysis of retrospectively collected data of 129 patients with NVAF from April 2000 to December 2005 at a single tertiary hospital. All patients were registered at the anticoagulation service.
  
  
  RESULTS
  The median duration of follow up was 2.03 years (interquartile range 1.35 - 2.96). During the follow-up period, 60.9 +/- 14.9% of the INR were within the target INR range. INR stability was not significantly different between patients without and with stroke (61.2 +/- 15.0% vs 53.3 +/- 4.9%). Among the known factors affecting fluctuations of the INR value, the most frequent factor was noncompliance (41.8%).
  
  
  CONCLUSIONS
  The present study showed that it was not enough to maintain INR values within the target range in warfarin-treated patients with NVAF even at a tertiary hospital. Noncompliance is an important problem which interferes with maintaining target INR range.
authors.affiliation: Division of Cardiology, Department of Medicine, Cardiac and Vascular Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Jun Hyung
authors.initials: JH
authors.lastname: Kim
authors.forename: Young Bin
authors.initials: YB
authors.lastname: Song
authors.forename: Dae Hee
authors.initials: DH
authors.lastname: Shin
authors.forename: Je Sang
authors.initials: JS
authors.lastname: Kim
authors.forename: Jin-Oh
authors.initials: JO
authors.lastname: Choi
authors.forename: Young Kun
authors.initials: YK
authors.lastname: On
authors.forename: June Soo
authors.initials: JS
authors.lastname: Kim
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000188:drug therapy* / Q000453:epidemiology / Q000209:etiology; D016903:Drug Monitoring / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006351:Heart Valves; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D010349:Patient Compliance; D012189:Retrospective Studies; D012307:Risk Factors; D013927:Thrombosis / Q000097:blood* / Q000453:epidemiology / Q000517:prevention & control*; D014859:Warfarin / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D014859:Warfarin