Point-of-Care INR Testing

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When a group of drugs called the “new oral anticoagulants” or “NOACs” recently became available in Canada, many felt that it would be the end of an era for . Warfarin had been used for over 60 years to prevent blood clots and stroke in patients at increased risk, and it is safe and effective. But dietary restrictions and the need for regular blood monitoring can make warfarin therapy challenging – challenges that don’t exist with the NOACs. However, the NOACs cost significantly more than warfarin even when the cost of blood monitoring is factored in. And clinician and patient experience with the newer drugs is limited.

To help physicians and patients make informed decisions about medications for blood clot and stroke prevention, a review of the medical evidence was needed. And, after all of the medical evidence on warfarin and the NOACs was reviewed by – an independent, evidence-based health technology agency, a panel of experts recommended that warfarin remain the first choice for the prevention of blood clots and stroke in patients with atrial fibrillation. The NOACs were recommended as a second-line option for some patients.

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But the experts also recommended that to maximize the benefits of warfarin, a structured treatment plan should be followed, including regularly scheduled blood tests to monitor therapy, the use of dosing tools, patient education, and the involvement of caregivers and health care professionals.

CADTH has just completed another research project looking more closely at the issue of regular blood tests to monitor warfarin therapy. When taking warfarin, patients must be monitored to ensure that they are getting the right amount of the medication and are not at risk for bleeding or blood clots. The standard method for monitoring the drug therapy is testing of blood drawn from a patient at a lab to measure the INR (which stands for “international normalized ratio” and is a measure of the time it takes a patient’s blood to form clots). However, point-of-care – testing the blood not at a lab but instead where the patient is already located – is another way of monitoring warfarin therapy.

Point-of-care INR testing is similar to the way patients with diabetes test their blood sugar. A small sample of blood is obtained by pricking the fingertip. The blood is placed on a test strip and inserted into a device called a coagulometer, which analyses the blood and displays the INR result. Point-of-care INR testing provides quicker results than lab testing and can be more convenient for patients and their caregivers by removing the need to travel to a lab. This can be particularly helpful for patients in rural or remote areas who live long distances from lab facilities.

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Point-of-care INR testing can allow patients to manage their own warfarin dose adjustments using the testing results. This is called “patient self-management.” For patients unable to manage dose adjustments, they could use point-of-care INR testing to get their INR results and then call a health care professional who will then adjust their warfarin therapy as needed. This is referred to as “patient self-testing.” Alternatively, point-of-care INR testing could be used by health care professionals with their patients in a clinical setting such as family doctor’s office or anticoagulation clinic.

After reviewing all of the medical evidence on point-of-care INR testing for patients taking warfarin, an expert panel agreed that point-of-care INR testing is accurate. The experts recommended that patients should be offered, if they are willing and able, the option to test their own INRs and make dose adjustments to their medication.  The panel recognized that these patients will require ongoing education and support to ensure the success of their self-management of warfarin and that quality assurance of point-of-care INR testing is important.

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The expert panel also recommended that if patients are not willing or able to manage their own warfarin dose adjustments, self-testing of INR with dose adjustments by a health professional may be an option, but only if there are significant barriers to patients having their INR regularly tested in a lab. These barriers might include living in rural or remote areas far from a lab, or mobility issues that make travel  to a lab difficult.

The evidence also showed that using point-of-care INR testing in a clinic setting can be more costly than lab testing. This doesn’t rule out the use of point-of-care INR testing in doctor’s offices or anticoagulation clinics but does mean that careful consideration of a clinic’s context and costs are important when considering implementing point-of-care INR testing.

If you are a clinician, patient, caregiver, or health care decision-maker and would like more information on this project or other health technology assessments, you can find it all free of charge on our website at www.cadth.ca. Our information on warfarin, the NOACs, point-of-care INR testing, and other related topics can also be found at: www.cadth.ca/clots.