title: Should patient characteristics influence target anticoagulation intensity for stroke prevention in nonvalvular atrial fibrillation?: the ATRIA study.
abstract: BACKGROUND
  Randomized trials and observational studies support using an international normalized ratio (INR) target of 2.0 to 3.0 for preventing ischemic stroke in atrial fibrillation. We assessed whether the INR target should be adjusted based on selected patient characteristics.
  
  
  RESULTS
  We conducted a case-control study nested within the ATRIA cohort's 9217 atrial fibrillation patients taking warfarin to define the relationship between INR level and the odds of thromboembolism (TE; mainly stroke) and of intracranial hemorrhage (ICH) relative to INR 2.0 to 2.5. We identified 396 TE cases and 164 ICH cases during follow-up. Each case was compared with 4 randomly selected controls matched on calendar date and stroke risk factors using matched univariable analyses and conditional logistic regression. We explored modification of the INR-outcome relationships by the following stroke risk factors: prior stroke, age, and CHADS(2) risk score. Overall, the odds of TE were low and stable above INR 1.8. Compared with INR 2.0 to 2.5, the relative odds of TE increased strikingly at INR <1.8 (eg, odds ratio, 3.72; 95% CI, 2.67 to 5.19, at INR 1.4 to 1.7). The odds of ICH increased markedly at INR values >3.5 (eg, odds ratio, 3.56; 95% CI: 1.70 to 7.46, at INR 3.6 to 4.5). The relative odds of ICH were consistently low at INR <3.6. There was no evidence of lower ICH risk at INR levels <2.0. These patterns of risk did not differ substantially by history of stroke, age, or CHADS(2) risk score.
  
  
  CONCLUSIONS
  Our results confirm that the current standard of INR 2.0 to 3.0 for atrial fibrillation falls in the optimal INR range. Our findings do not support adjustment of INR targets according to previously defined stroke risk factors.
authors.affiliation: Clinical Epidemiology Unit, General Medicine Division, Massachusetts General Hospital, Boston, MA 02114, USA. dsinger@partners.org
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Singer
authors.forename: Yuchiao
authors.initials: Y
authors.lastname: Chang
authors.forename: Margaret C
authors.initials: MC
authors.lastname: Fang
authors.forename: Leila H
authors.initials: LH
authors.lastname: Borowsky
authors.forename: Niela K
authors.initials: NK
authors.lastname: Pomernacki
authors.forename: Natalia
authors.initials: N
authors.lastname: Udaltsova
authors.forename: Alan S
authors.initials: AS
authors.lastname: Go
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000188:drug therapy* / Q000453:epidemiology*; D002545:Brain Ischemia / Q000453:epidemiology / Q000517:prevention & control; D016022:Case-Control Studies; D016208:Databases, Factual; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D020300:Intracranial Hemorrhages / Q000453:epidemiology; D016015:Logistic Models; D008297:Male; D012307:Risk Factors; D020521:Stroke / Q000453:epidemiology* / Q000517:prevention & control*; D013923:Thromboembolism / Q000453:epidemiology / Q000517:prevention & control; D014859:Warfarin / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D014859:Warfarin