Quality metrics of warfarin initiation in hospitalized older adults

Abstract

Achieving therapeutic international normalized ratio (INRs) in warfarin naïve older adults can be complicated due to sensitivity factors. While multiple tools exist for warfarin initiation in the outpatient setting, there is a dearth of guidance for inpatient initiation. This study aims to: (1) describe a large health system's initiation warfarin quality metrics in older inpatients, defined by INR overshoots greater than or equal to 5.0; (2) identify intrinsic and extrinsic patient factors associated with overshoots; and (3) explore the association between inpatient overshoots and clinical outcomes. Data on inpatients ≥ 65 years initiated on warfarin 1/1/2014-6/30/2016 were extracted through retrospective chart review. The primary outcome was prevalence of overshoots (INR ≥ 5). Logistic regression modeling determined the risk factors for overshoots. Multivariate analysis was employed to associate overshoots with length of stay (LOS), bleeding, and mortality. Additional analysis of the impact of patient weight (kg) on overshoots was achieved through chi square analysis. Of 4556 inpatients initiated on warfarin, 8% experienced overshoots. Non-black race, peripheral vascular disease, chronic obstructive pulmonary disease (COPD), mild liver disease, low weight, and no statin use were found to be predictive of overshoots. Compared to the group without overshoots, the group with overshoots experienced a significantly increased LOS (13 days vs. 8 days, < 0.001), higher bleed rate (30.1% vs. 6.5%, adjusted OR 6.2, p < 0.001), and higher mortality rate (13.8% vs. 3.4%, adjusted OR 4.4, p < 0.001). Inpatient warfarin initiation was associated with frequent overshoots and poor outcomes. Future studies should focus on strategies to improve hospital warfarin initiation safety.

Keywords: Adverse drug events; Anticoagulants; INR; Inpatients; Warfarin; Warfarin initiation.