Updated January 2020

Patients on warfarin need to get their INR levels measured regularly. This often involves visiting a local anticoagulation clinic or healthcare provider. However, in-home testing, also known as self-testing or point-of-care testing, is a great option that many patients are unaware of.

“I think a lot of patients don’t think of it 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. Dr. Collins works at the anticoagulation clinic at Brigham and Women’s 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 is no specific reason for why in-home testing isn’t advertised to patients. “I think education would definitely make more patients aware.”

PT/INR monitoring system

How does INR in-home testing work?

  1. If you’re interested in in-home testing, you must speak to the provider who prescribes your warfarin and manages your anticoagulation. Your provider will help you decide if you’re a good fit for in-home testing. If so, your provider will submit a form to a medical service company with your information. There are several companies that provide these machines. According to Dr. Collins, Brigham and Women’s Hospital works primarily with Alere to provide their patients with in-home testing services.
  1. The medical service company will get you set up with your machine and show you how to use it properly. “Once the patient is determined to be a good candidate for self-testing, we go through a company that handles the testing of the INR results and the training,” explained Dr. Collins. “They send a trainer out to your home and review how to use the machine correctly and report the results. They’ll also work with your health insurer to cover the cost of the machine.”
  1. Once you’re are set up with your device and you’re properly trained to monitor and report your INR levels, you’re ready to take over your own INR testing. When you report your INR results, the anticoagulation clinic will make dosage adjustments as needed.

Who’s a good candidate for in-home testing?

INR in-home testing is a great resource that’s beneficial for many patients. Dr. Collins estimates that 15-20% of his patients at Brigham and Women’s Hospital self-test.

In-home testing is a great option for patients who can’t make it to the lab frequently, who travel often, or who want to be self-sufficient. It’s also good for patients who have difficulty leaving their homes. Patients must be on warfarin for 3 months before in-home testing can be approved by insurance. 

“Most patients think of this as a no-brainer. It’s something that’s more convenient. You don’t have to give a full blood sample (just a finger stick). It’s much less invasive,” said Dr. Collins. However, he noted that in-home testing is not for everyone.

“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 as an example. “For those patients, we would want to avoid point-of-care testing.”

What benefits come with in-home testing?

  • In-home testing is convenient.
  • It allows patients to test their INR levels without the need for frequent visits to a lab.
  • In-home testing only requires a finger stick, instead of a full blood sample.

In-home testing may lead to fewer blood clots

Studies show that patients who self-test are more often in the correct INR range then those who don’t. They spend closer to 71% of their time in range, compared to patients who visit anticoagulation clinics and spend 60-65% of their time in range.

“The time in range is much better in patients who self-test,” Dr. Collins noted. “The occurrence of adverse thrombotic events is also decreased in this population.”

Self-testers’ staying in range could be related to how often they have their INR levels tested. Insurance mandates that they are tested at least twice a month. This leads them to receiving more frequent dosage adjustments to balance their INR levels.

Dr. Collins also noted that this difference in INR range may stem from the types of patients who seek out in-home testing and shepherd it through the approval process. These patients are often highly motivated and invested in their healthcare. They take their treatments seriously, strictly adhering to their treatment plans.

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. “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.”

Although self-testing machines are approved by the FDA, Brigham and Women’s Hospital tests the accuracy of the machines themselves. Dr. Collins has found that some of his patients’ machines can be up to 20-30% off in measuring INR levels. To counteract this, Brigham and Women’s Hospital compares the results of the patients’ first few in-home tests with tests taken at the clinic.

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.