Talk to the Veterans Crisis Line now
U.S. flag
An official website of the United States government

VA Health Systems Research

Go to the VA ORD website
Go to the QUERI website
Publication Briefs

Study Suggests Risk-Adjusted Time in Therapeutic Range Can Be Used as Quality Indicator for Outpatient Oral Anticoagulation

Oral anticoagulation is a highly effective therapy for patients with atrial fibrillation, venous thromboembolism, and mechanical heart valves. However, the quality of this therapy needs to be measured to ensure that the benefits of anticoagulation are maximized and the harms minimized. The percent of time in therapeutic range (TTR) may be a good quality measure because it can be calculated from automated data, it can be improved, and it has been linked to important outcomes. This study examined the suitability of risk-adjusted TTR as a potential quality indicator for anticoagulation therapy among VA patients. The risk-adjusted model incorporated many potential variables such as demographics, driving distance to care, and comorbid mental and physical health conditions. Using VA data, investigators identified 124,551 Veterans who received outpatient oral anticoagulation therapy (warfarin) from 100 VA anticoagulation clinics for indications other than valvular heart disease between 10/06 and 9/08. Investigators sought to answer three questions: Does mean TTR differ among sites of care? Does risk-adjusting TTR meaningfully alter site rankings? And, would risk-adjusted site rankings be relatively constant from year to year, suggesting that TTR is measuring quality of care rather than statistical variation only?


  • Risk-adjusted time in therapeutic range (TTR) can be used to profile the quality of outpatient oral anticoagulation in a large, integrated healthcare system. Thus, this measure can serve as the basis for quality measurement and quality improvement efforts.
  • TTR differed among VA anticoagulation clinics – from 38% to 69%, or from poor to excellent.
  • Risk-adjustment did not alter performance rankings for many sites, but for other sites it made an important difference. For example, the anticoagulation clinic that was ranked 27th out of 100 before risk adjustment was ranked as one of the best (7th) after risk-adjustment.
  • Risk-adjusted site rankings were consistent between the first and second years of the study, suggesting that risk-adjusted TTR measures a construct (quality of care) that is stable over time.


  • The risk-adjustment model used in this study did not include some factors that contribute to variability in TTR, particularly diet and adherence to therapy.
  • Due to strict requirements for complete data, investigators were unable to profile performance at some VA anticoagulation clinics.

This research was supported by an HSR&D Career Development Award to Dr. Rose. Drs. Rose, Ozonoff, Berlowitz, and Mr. Reisman are part of HSR&D’s Center for Health Quality, Outcomes, and Economics Research in Bedford, MA.

PubMed Logo Rose A, Hylek E, Ozonoff A, Ash A, Reisman J, Berlowitz D. Risk-Adjusted Percent Time in Therapeutic Range as a Quality Indicator for Outpatient Oral Anticoagulation: Results of the Veterans AffaiRs Study to Improve Anticoagulation (VARIA). Circulation: Cardiovascular and Quality Outcomes 2011 Jan 1;4(1):22-29.

Related Briefs

» next 91 Heart Disease Briefs...

» next 172 Medication Briefs...

» next 136 Quality Briefs...

What are HSR Publication Briefs?

HSR requires notification by HSR-funded investigators about all articles accepted for publication. These journal articles are reviewed by HSR and publication briefs or summaries are written for a select number of articles that are then forwarded to VHA Central Office leadership to keep them informed about important findings or information. Articles to be summarized are selected by HSR based on timeliness of the findings, interest of leadership, or potential impact on the organization. Publication briefs are written for only a small number of HSR published articles. Visit the HSR citations database for a complete listing of HSR articles and presentations.

Questions about the HSR website? Email the Web Team

Any health information on this website is strictly for informational purposes and is not intended as medical advice. It should not be used to diagnose or treat any condition.