The quality of warfarin prescribing and monitoring in Veterans Affairs nursing homes

Abstract

Objectives: To describe the quality of warfarin prescribing and monitoring in Veterans Affairs (VA) nursing homes and to assess the factors associated with maintaining a therapeutic international normalized ratio (INR).

Design: Retrospective cohort.

Setting: Five VA nursing homes.

Participants: All veterans who received warfarin between January 1 and June 30, 2008, at the nursing homes.

Measurements: Using medical records, the percentage of person-time spent in the target INR range, the proportion of patients with INRs in the therapeutic range on 50% or more of their person-days, and the frequency of INR monitoring were estimated. Multivariable logistic regression was used to identify factors associated with maintaining a therapeutic INR 50% or more of the time.

Results: Over 6 months, 160 patients received 10,380 person-days of warfarin. INRs were in the therapeutic range for 55% of the person-days, and 99% of the INR tests were repeated within 4 weeks of the previous result. On an individual level, 49% of patients had INRs in the target range for 50% or more of their person-days. Achieving this outcome was more likely in patients with prevalent warfarin use than with new use (adjusted odds ratio (AOR)=2.86, 95% confidence interval (CI)=1.06-7.72). Conversely, patients with a history of a stroke (AOR=0.38, 95% CI =0.18-0.80) were less likely to have therapeutic INRs for 50% or more of their days.

Conclusion: Warfarin appears to be prescribed and monitored effectively in VA nursing home patients. Future studies should focus on increasing time in therapeutic range in patients with poor INR control.