Risk-Adjusted Percent Time in Therapeutic Range as a Quality Indicator for Outpatient Oral Anticoagulation

Abstract

Oral anticoagulation is safer and more effective when patients receive high-quality care. However, there have been no prior efforts to measure quality of oral anticoagulation care or to risk adjust it to ensure credible comparisons. Our objective was to profile site performance in the Veterans Health Administration (VA) using risk-adjusted percent time in therapeutic range (TTR). We included 124 551 patients who received outpatient oral anticoagulation from 100 VA sites of care for indications other than valvular heart disease from October 1, 2006, to September 30, 2008. We calculated TTR for each patient and mean TTR for each site of care. Expected TTR was calculated for each patient and each site based on the variables in the risk adjustment model, which included demographics, comorbid conditions, medications, and hospitalizations. Mean TTR for the entire sample was 58%. Site-observed TTR varied from 38% to 69% or from poor to excellent. Site-expected TTR varied from 54% to 62%. Site risk-adjusted performance ranged from 18% below expected to 12% above expected. Risk adjustment did not alter performance rankings for many sites, but for other sites, it made an important difference. For example, the site ranked 27th of 100 before risk adjustment was one of the best (risk-adjusted rank, 7). Risk-adjusted site rankings were consistent from year to year (correlation between years, 0.89). Risk-adjusted TTR can be used to profile the quality of outpatient oral anticoagulation in a large, integrated health system. This measure can serve as the basis for quality measurement and quality improvement efforts.