INR targets and site-level anticoagulation control: results from the Veterans AffaiRs Study to Improve Anticoagulation (VARIA)

UMMS Affiliation

Department of Quantitative Health Sciences

Publication Date


Document Type



Administration, Oral; Aged; Anticoagulants; Blood Coagulation; Drug Monitoring; Female; Guideline Adherence; Healthcare Disparities; Humans; International Normalized Ratio; Male; Middle Aged; Physician's Practice Patterns; Practice Guidelines as Topic; Predictive Value of Tests; Quality Indicators, Health Care; Time Factors; United States; United States Department of Veterans Affairs


Cardiovascular Diseases | Epidemiology | Health Services Research


BACKGROUND: Not all clinicians target the same International Normalized Ratio (INR) for patients with a guideline-recommended target range of 2-3. A patient's mean INR value suggests the INR that was actually targeted. We hypothesized that sites would vary by mean INR, and that sites of care with mean values nearest to 2.5 would achieve better anticoagulation control, as measured by per cent time in therapeutic range (TTR).

OBJECTIVES: To examine variations among sites in mean INR and the relationship with anticoagulation control in an integrated system of care.

PATIENTS/METHODS: We studied 103,897 patients receiving oral anticoagulation with an expected INR target between 2 and 3 at 100 Veterans Health Administration (VA) sites from 1 October 2006 to 30 September 2008. Key site-level variables were: proportion near 2.5 (that is, percentage of patients with mean INR between 2.3 and 2.7) and mean risk-adjusted TTR.

RESULTS: Site mean INR ranged from 2.22 to 2.89; proportion near 2.5, from 30 to 64%. Sites' proportions of patients near 2.5, below 2.3 and above 2.7 were consistent from year to year. A 10 percentage point increase in the proportion near 2.5 predicted a 3.8 percentage point increase in risk-adjusted TTR (P < 0.001).

CONCLUSIONS: Proportion of patients with mean INR near 2.5 is a site-level 'signature' of care and an implicit measure of targeted INR. This proportion varies by site and is strongly associated with site-level TTR. Our study suggests that sites wishing to improve TTR, and thereby improve patient outcomes, should avoid the explicit or implicit pursuit of non-standard INR targets.

DOI of Published Version



J Thromb Haemost. 2012 Apr;10(4):590-5. doi: 10.1111/j.1538-7836.2012.04649.x.

Journal/Book/Conference Title

Journal of thrombosis and haemostasis : JTH

PubMed ID


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Link to article in PubMed