02 May 0
Weekly INR self-testing is an accurate and effective way to manage warfarin and Coumadin therapy, suggested new research. While this is not the first study to find that patients who partake in home monitoring spend more time within their “safe therapeutic range” and have less complications with their anticoagulation therapy, it is the largest retrospective study of real-world self testers and the first to compare weekly INR testing to variable testing.
Overall, the clinical evidence from the study involving 29,457 patients followed over 2.5 years demonstrated that more frequent testing improves patient safety and decreases the risk of major thomboembolic and bleeding events. Patients testing their INR weekly achieved a significantly greater TTR (Time in Therapeutic Range) of 74% vs. 68.9% for patients self testing every 2-4 weeks. The study also stated that “Weekly testers experienced significantly fewer critical values (INR <1.5 or >5.0) than did variable testers”.
Understanding what’s considered good TTR in the real-world is important in grasping the importance of these findings, according to Dr. Ansell. “Clinical trials have established that 65% TTR is considered acceptable,” he explained. “Unfortunately, most patients on warfarin management hover around 55%. So the outcome here is outstanding.”
Patients prescribed for PST (Patient Self Testing) must be reliable to report their test results, and willing and able to test their INR with a monitor at home with a simple finger stick. Their physician submits a prescription form to an IDTF (Independent Diagnostic Testing Facility) for the service and insurance is verified. Patients then must undergo a FDA and Medicare required face-to-face training on how to utilize the meter and report test results. Physicians are then sent all INR results in order to manage the patient’s Coumadin therapy.
In all age groups involved in the study, patients testing weekly outperformed patients testing every 2-4 weeks. Additionally, the study found that patients 75 years and older that tested weekly had a mean TTR of more than 73%. The researchers stated that the results of self-testing for the elderly are significant as they are often at the highest risk of bleeding during Coumadin therapy.
The study also brought to light the flawed comparison of trials performed by the drug makers of the new anticoagulants, Eliquis, Xarelto, and Pradaxa. Results from the STABLE Study noted that even patients who tested their INRs the least frequently performed significantly better than the top-performing patients treated with warfarin in trials involving the new oral anticoagulants. Thus if patients in the new anticoagulant trials taking Pradaxa, Xarelto, or Eliquis were compared to any of the self testing groups from the STABLE Study they would have found warfarin coupled with self INR testing to be a superior and safer method of anticoagulation therapy for patients in all circumstances.
In the United States approximately 3 million people are on warfarin, but only about 120,000 people test their INR at home, according to Dr. Ansell. He said the slow growth of self-testing could be due to a lack of physician awareness, their belief that patients can not test properly on their own, or that physicians’ may perceive that self-testing is inaccurate. This study showed otherwise. “We demonstrated that the average patient on warfarin can monitor their INRs at home, and do it very well,” he said. “We’ve shown that self-testing is a reasonable and feasible means of practice.”
The study was published online in the American Journal of Managed Care and the full PDF article can be viewed HERE.
1. DeSantis G, Hogan-Schlientz J, Liska G, et al. STABLE results: warfarin home monitoring achieves excellent INR control. Am J Manag Care. 2014;20(3):202-209.