Trends in Warfarin Monitoring Practices Among New York Medicare Beneficiaries, 2006-2011.

Anticoagulation with warfarin requires frequent evaluation of the international normalized ratio (INR), and less invasive testing devices are available for use by clinicians at the point-of-care (POC) and by patients who self-test (PST). Despite commercial availability and positive results of published studies, evidence suggests that adoption of less invasive (POC/PST) testing in the United States is slow. Considering the equivalence of results and logistical advantages of POC/PST testing, slow uptake may indicate a gap in quality of care warranting evaluation and possibly intervention. This study used Medicare fee for service claims data to explore the uptake of POC/PST INR monitoring across New York State over a 6 year time frame (2006-11), with additional analyses based on beneficiary age, sex, race and ethnicity and income by county. In 2006, only 28.3% of 103,410 analyzable beneficiaries presumed to be chronic warfarin users based on INR testing patterns were monitored by POC/PST, and increased to only 37.6% by 2011. Utilization of POC/PST testing varied widely by county (baseline range 1.2-89.4%), and uptake of these testing modalities in New York State was significantly lower among the very elderly, women, and ethnic minorities. We hypothesize that poor penetration of these less invasive INR testing modalities into highly populated New York City and barriers to POC utilization in long term care facilities may account for a portion of the variability in INR testing patterns observed in this study. However, additional research is needed to further explore whether disparities in warfarin monitoring practices exist.