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

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.