How to measure inr for warfarin?
Patients on warfarin need to get their INR levels measured regularly, which often involves visiting a local anticoagulation clinic, lab, or doctor’s office to get a blood test. However, there’s another option for INR testing: in-home testing, also known as self-testing or point-of-care testing.
“I think a lot of patients don’t think of home testing as an option because they don’t really know about it,” explained Dr. Peter Collins, an Advanced Clinical Practice Pharmacist at Brigham and Women’s Hospital (BWH). Dr. Collins works in the anticoagulation clinic at BWH and helps patients on warfarin get set up with in-home INR testing.
“Doctors’ offices, and even sometimes the anticoagulation clinics, don’t necessarily present in-home testing as an option,” he continued, acknowledging that there’s no specific reason for why in-home testing isn’t advertised more frequently to patients. “I think education would definitely make more patients aware.”
What benefits come with in-home testing?
Self-testing patients typically check their levels more often than patients who go to the lab, so they’re more likely to have their warfarin dosage adjusted as needed to stay in the correct INR range. Dr. Collins also noted that this increase in time within therapeutic range may also be influenced by the types of patients who seek out in-home testing. “These patients are often highly motivated and invested in their healthcare, which leads to strict adherence to their treatment plans,” he explains.
Who’s a good candidate for in-home testing?
In-home testing is a good option for patients who can’t make it to the lab frequently, who travel often, who have difficulty leaving their homes, or who want to be more independent. Whatever your reason for switching to home testing, the key is that you remain committed to testing your levels.
“When a patient shows interest in in-home testing, we look at the indication for their anticoagulation. There are some blood disorders that interfere with how the machine measures the INR ratings,” he explained, citing antiphospholipid syndrome (APLS) as an example. “For those patients, we would want to avoid point-of-care testing.”
How do I get started with home INR testing?
If you’re interested in in-home testing, you must speak to the provider who manages your warfarin. They will work with you to decide if you’re a good fit for in-home testing. If you are, they’ll submit a form to a medical service company with your information. There are several companies that provide the machines and patient training, including Acelis, Roche, and RCS.
“Once you’re determined to be a good candidate for self-testing, your provider or pharmacy team will go through a company that handles training and INR test results,” explained Dr. Collins. “Typically, these companies send a trainer out to your home to review how to use the machine correctly and help you report the results for the first time.” Trainings can also be done virtually. In the midst of the COVID-19 pandemic, all trainings have shifted to a virtual platform.
“The testing machines themselves only have two buttons and are pretty easy to use. Patients who have diabetes will be familiar with this type of machine – it follows the same process as testing blood sugar. The most important thing is to make sure that you get enough blood on the test strip,” says Dr. Collins.
After testing your blood, you’ll have to report the results to the company you’re working with. Most patients use an app or a website to send in their reports. Once the company gets the result, they’ll send it to your provider. The company will also manage billing and the insurance-related parts of the process. When your provider receives your results, they can make dosage adjustments as needed.
There are several other important points to note before you transition to home testing:
Are there any challenges to in-home testing?
In-home testing is not for everyone, and it does come with challenges. One major issue is that the in-home testing machines can be less accurate than testing at a clinic. Dr. Collins has found that some machines can be up to 20-30% off in measuring INR levels. “It’s not as accurate as a hospital blood draw, but we have additional tools to ensure we’re getting the most accurate result,” said Dr. Collins. “We have policies in place to help with that.” Patients who self-test must also understand that they may have to return to the clinic for testing if their INR levels are found to be high.
As with all forms of treatment and testing, INR in-home testing has benefits and challenges. It’s not the appropriate testing method for every patient. Talk to your healthcare provider if you’re interested in pursuing in-home testing.
It can be monitored by drawing blood from a vein and sending the blood to an accredited laboratory to test, or it can be monitored by testing blood from a fingerstick with an INR test meter outside of a laboratory.
INR test meters and test strips are medical devices regulated by the U.S. Food and Drug Administration. The FDA wants to ensure patients and health care providers use these devices safely. Please read on for more information.
Warfarin (also known by the brand names Coumadin and Jantoven) is a blood thinner prescribed to prevent and treat blood clots. Warfarin therapy may be prescribed for patients with certain types of irregular heartbeat, blood clots in the legs or lungs, and patients who have certain medical device implants such as artificial heart valves.
A patient’s warfarin dose depends on many factors, including the patient’s age, overall health and genetic makeup. The dose may also need to be adjusted based on a patient’s diet and current medications.
Warfarin must be monitored to ensure it is working effectively and being used safely. Achieving the correct warfarin dosage can be difficult but is extremely important. If the dose of warfarin is too low, the patient is at risk of developing harmful blood clots. If the dose of warfarin is too high, the patient may be at risk of serious bleeding. It can be monitored by drawing blood from a vein and sending the blood to an accredited laboratory to test, or it can be monitored by testing blood from a fingerstick with an INR test meter outside of a laboratory. INR test meters may be prescribed to patients for use in the home, and they may also be used by health care providers at the point of care, such as a health care setting.
How often an INR test meter is used to monitor warfarin, and the results a patient should expect, will be based on recommendations from the patient’s health care provider. An INR target range is set by a health care provider. It is typically between 2.0 and 3.0 for basic blood-thinning needs, though the range may vary based on a patient’s specific conditions. An INR above the patient-specific target range may increase the risk of bleeding, while an INR below the target range may increase the risk of developing a blood clot. Patients should work with their health care provider to develop a plan for achieving and maintaining a target INR; recognize when there is a problem; and know when to contact their health care provider.
The information and resources on this website are intended to provide useful information for patients and caregivers who are using INR test meters in the home and for health care providers using INR test meters in a clinical setting.
Home Users - Patients and Caregivers: For more information and tips on using an INR test meter to monitor warfarin safely and effectively, visit Tips for Patients and Caregivers Using INR Test Meters at Home.
Health Care Providers: For more information and tips on using an INR test meter to monitor warfarin safely and effectively, visit Tips for Health care Providers Using INR Test Meters in a Clinical Setting.
All health care providers, patients and caregivers, are strongly encouraged to voluntarily report INR test meter problems directly to the FDA through MedWatch, the FDA’s voluntary reporting program. Problems should be reported whenever one suspects there is an issue with an INR test meter such as a malfunction or incorrect result, or that the meter caused or contributed to a serious injury or death. Hospitals, nursing homes, coagulation clinics, and outpatient facilities should follow the reporting procedures established by their facilities. INR test meter users should also report these problems to the manufacturer using the phone number listed on your meter’s instructions.
When submitting a report through MedWatch, please include as much of the following information as possible:
The following are examples of some of the problems that may arise and should be reported:
Related Resources:
The international normalised ratio (INR) blood test tells you how long it takes for your blood to clot.
A test called the prothrombin time (PT) actually measures how quickly your blood clots. The PT results can be expressed as an INR to standardise the results. This is done when the test is used to monitor treatment with a medicine called warfarin.
INR tests are used in people taking warfarin — a medicine that treats and prevents blood clots.
Warfarin is prescribed for some people to:
Your doctor uses your INR results to work out what dose of warfarin you should take. You need to take enough warfarin to reduce your risk of blood clots. But not so much that you are at risk of serious bleeding. This is your ‘target INR range’.
The prothrombin test can also be used to:
No special preparation is needed for this test.
If your INR test result is above your target range, it means your blood is clotting too slowly, and there is a risk of bleeding.
If your INR test result is below your target range, it means you are at increased risk of a blood clot.
Tell your doctor about:
That’s because these can affect the way that warfarin works and your INR result.
Warfarin can cause life-threatening bleeding. If your INR is too high, you are at increased risk of bleeding. Depending on your INR and risk of bleeding, your doctor may:
Close monitoring is needed until your risk of bleeding is reduced.
If your INR is too low, your risk of blood clots is increased. Your doctor will need to adjust your dose to reach your target INR range.
Some of the newer anticoagulant medicines do not need to be monitored frequently with INR blood tests.
Talk to your doctor about the different types of anticoagulants and whether you will need an INR blood test.
Pathology Tests Explained has more information about Prothrombin time and INR testing.
You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available 24 hours a day, 7 days a week.
You also can get similar guidance from a POC device manufacturer or an Independent Diagnostic Testing Facility (IDTF) or distributor that provides patient services connected to at-home INR testing. Most of these IDTFs will require that your doctor send them your self-testing prescription, as well as your relevant medical information, to enroll you in their service.
IDTFs can play a valuable role in your self-testing efforts, as they can help you verify your insurance or Medicare coverage, provide training to help improve your self-testing skills, help manage your testing results, and ensure that your test results routinely reach your healthcare professional.
Below is an alphabetical listing of several different device manufacturers, IDTFs, and patient services that you can explore for more information and guidance:
Acelis Connected Health, an Abbott Company, provides an end-to-and service for PT/INR management with support for both patients and their physicians. You can learn more about Acelis Connected Health and their service by reading the frequently asked questions that appear on their website here.
Advanced Cardio Services is an IDTF that provides a home anticoagulation testing and monitoring service to help reduce the risk of potential complications associated with long-term warfarin therapy or out-of-range INR levels. You can learn more about INR self-testing through this service by reading the frequently asked questions that appear on their website here.
CoaguChek® and CoaguChek® Patient Services is a service of Roche Diagnostics. Roche Diagnostics manufactures and sells a broad spectrum of diagnostic equipment and supplies, including the CoaguChek® XS device for INR self-testing. To learn more about this company’s INR self-testing devices and patient home-testing services, you can begin by reading the information that appears on their CoaguChek® Patient Services website here.
mdINR is a Lincare company, and an IDTF that provides equipment and services for patients who perform INR at-home self-testing. You can learn more about their services by reviewing the frequently asked questions posted to their website here.
RCS is an IDTF that supports the INR self-testing needs of clinicians and patients. You can learn more about INR self-testing through this service by reading the frequently asked questions that appear on their website here.
