More Time in Therapeutic Range

According a CMS Decision Memo based on 11 studies with over 2000 patients, PT/INR self testing significantly improves time in therapeutic range (TTR) for select groups of patients, compared to testing done in physician offices or anticoagulation clinics.

Time in Therapeutic Range
Increases with More Frequent Testing
Clinical Study TTR Frequncy of Testing
Gottlieb 1994 50% 25 days
Horstlotte 59% 19 days
Cannegeiter 1995 61% 18days
Ansell 1995 66% 16 days
Palaretti 1996 68% 15 days
Ansell 1995 89% 13 days
Horstkotte 1988 92% 4 days

According to the CMS Decision Memo:

  • The studies are consistent in demonstrating that the use of the home INR monitor significantly increases TTR. There was no study that showed these home devices resulted in decreased, or equivalent TTR. The studies — which were conducted by different investigators at different sites, with different patient populations, and spread over a decade — were all consistent.
  • Testing at home allows not only for an increased frequency of testing, but also improved timeliness, providing the ability to perform the test when it is needed. In addition, the data showed less fluctuation in values.

The Society of Thoracic Surgeons/American Association for Thoracic Surgery (STS/AATS) also supports Medicare coverage of home PT/INR testing for the following reasons:

  • The safety and effectiveness of warfarin therapy is optimized when INR values are properly maintained within a target therapeutic range. As the distance from a target INR value increases or decreases, the likelihood of adverse events also increases, thus maintaining a therapeutic range is vital for patient well-being.
  • Patient self-testing for mechanical heart valve patients would improve patient outcomes. The cost of complications from mechanical heart valve patients is high and may require additional surgical intervention and hospitalization cost to replace a thrombosed valve or treat a bleeding event.
  • Studies have shown that by empowering warfarin patients to perform PT/INR self-testing, more patients spend a higher proportion of time within their target INR range leading to fewer adverse effects.