Inventi Impact: Clinical Research

Inventi:pcr/16959/15

Out-of-range INR Values and Outcomes among New Warfarin Patients with Non-valvular Atrial\nFibrillation

Background Although efficacious in stroke prevention\nin non-valvular atrial fibrillation, many warfarin\npatients are sub-optimallymanaged. Objective To evaluate the\nassociation of international normalized ratio control and clinical\noutcomes among new warfarin patients with non-valvular\natrial fibrillation. Setting Adult non-valvular atrial fibrillation\npatients (C18 years) initiating warfarin treatment were selected\nfrom the US Veterans Health Administration dataset\nbetween 10/2007 and 9/2012. Method Valid international\nnormalized ratio values were examined from the warfarin\ninitiation date through the earlier of the first clinical outcome,\nend of warfarin exposure or death. Each patient contributed\nmultiple in-range and out-of-range time periods. Main outcome\nmeasure The relative risk ratios of clinical outcomes\nassociated with international normalized ratio control were\nestimated. Results 34,346 patients were included for analysis.\nDuring the warfarin exposure period, the incidence of events\nper 100 person-years was highest when patients had international\nnormalized ratio\\2:13.66 for acute coronary syndrome; 10.30 for ischemic stroke; 2.93 for transient ischemic attack;\n1.81 for systemic embolism; and 4.55 for major bleeding.\nPoisson regression confirmed that during periods with international\nnormalized ratio\\2, patients were at increased risk of\ndeveloping acute coronary syndrome (relative risk ratio: 7.9;\n95 % confidence interval 6.9ââ?¬â??9.1), ischemic stroke (relative\nrisk ratio: 7.6; 95 % confidence interval 6.5ââ?¬â??8.9), transient\nischemic attack (relative risk ratio: 8.2; 95 % confidence\ninterval 6.1ââ?¬â??11.2), systemic embolism (relative risk ratio: 6.3;\n95 %confidence interval 4.4ââ?¬â??8.9) and major bleeding (relative\nrisk ratio: 2.6; 95 %confidence interval 2.2ââ?¬â??3.0). During time\nperiods with international normalized ratio[3, patients had\nsignificantly increased risk of major bleeding (relative risk\nratio: 1.5; 95 % confidence interval 1.2ââ?¬â??2.0). Conclusion In a\nVeterans Health Administration non-valvular atrial fibrillation\npopulation, exposure to out-of-range international normalized\nratio values was associated with significantly increased risk of\nadverse clinical outcomes.