INR self-testing option create new opportunities for laboratorians

July 24, 2018

Laboratorians in modern healthcare organizations are under sustained pressure to keep improving the quality of the care they provide while maximizing every dollar they spend. Yet current industry trends may limit the clinical lab’s ability to operate at peak efficiency while supporting the delivery of personalized care.

Advancements in technology now allow sophisticated testing, once unique to the lab, to be performed in point-of-care (POC) settings or even at home. Laboratorians can embrace these changes as opportunities to help the system gain efficiencies and provide the personalized care that patients desire.

One of the best examples of this trend is INR (international normalized ratio) testing for patients who need long-term oral anticoagulation management. For many years, warfarin has been the only option for those patients. Because warfarin has a narrow therapeutic window, warfarin patients require close monitoring with INR testing. Recently, several direct oral anticoagulants (DOACs) have appeared on the market, offering new choices for patients without the need for monitoring and providing newfound freedom from scheduling appointments, lab testing, and clinic visits. However, these drugs may not be appropriate for everyone on long-term oral anticoagulation therapy.

In addition, the availability of a self-testing option has made INR monitoring much more convenient for patients who must or prefer to remain on warfarin. It’s important for laboratorians to educate themselves about each available testing option — lab, point-of-care, and self-testing — in order to offer sound recommendations to caregivers and healthcare administrators, demonstrating value to both health systems and patients.

Background on INR self-testing

Part of the World Health Organization Model List of Essential Medicines,1 warfarin remains a relevant tool in the overall scope of oral anticoagulation therapy. According to recent prescription data for all anticoagulants, nearly half of patients who are prescribed oral anticoagulants use warfarin.2 For this group, monitoring is required to ensure achievement of a therapeutic INR—typically, between 2.0 and 3.0.3 INR monitoring can occur at a lab, at the POC during a clinic visit, or in the patient’s home.

Similar to patients with diabetes mellitus who perform their own blood glucose testing, patients on warfarin have the ability to remotely monitor their INR using a finger-stick blood sample and a handheld meter in the home. A caregiver can perform the test, or patients can perform the test themselves. Results are then forwarded via various communication methods, including phone and wireless Bluetooth, to a provider who can quickly determine whether medication dosage adjustments are needed. Patients with diabetes can use their blood glucose test results to self-manage their own medications and treatment, but warfarin patients who self-test must still rely on advice from a provider to make changes.

The practice of self-testing at home to monitor warfarin patients isn’t yet commonplace, although it is in a position to become more mainstream. Several providers offer INR self-testing (that is, they furnish FDA-cleared handheld meters and strips, receive test results from patients, and relay results to physicians), and the services are often covered by private insurance and Medicare.

Advantages of self-testing

Many warfarin patients find the ability to monitor their own INR levels appealing for several reasons. First, the convenience of being able to test at home, at work, on vacation or anywhere else with a finger stick as opposed to a venous blood draw reduces the need for repeated visits to a provider’s office or lab, saving time, discomfort, and transportation-related expenses. As with in-office testing, doctors are able to receive the results quickly, making it easier for patients to immediately comply with dosage adjustments as needed.

Self-testing empowers patients with the tools and support they need to take a proactive role in their own healthcare with increased convenience and improved satisfaction. Data show that self-testing can improve a patient’s time in therapeutic range,4 an important factor in measuring compliance and the success of warfarin therapy.

DOACs vs. warfarin

While DOACs do offer value for many patients by eliminating the need for INR monitoring, there are some patients for whom warfarin remains the more appropriate course of action. Certain medical conditions, such as valvular atrial fibrillation, leading to the need for oral anticoagulant use, may make some patients ineligible for DOACs, resulting in the continued need for warfarin therapy.3

Additionally, some patients find personal comfort and reassurance in being able to know and monitor their own INR, or they may be unable to tolerate a DOAC. Pricing can be another consideration. Warfarin is available as a generic alternative, but currently DOACs are not, limiting those patients who are on DOACs to brand-name products and potentially higher out-of-pocket costs. A recent study using a model to simulate cost of care of a DOAC versus warfarin treatment suggests that warfarin is the most cost-effective oral anticoagulation treatment in the prevention of stroke and systemic embolism in patients with atrial fibrillation with a high risk of bleeding and who can achieve a TTR (time in therapeutic range) of at least 70 percent with warfarin.5

What self-testing means for labs

As the practice of INR self-testing becomes more common, it will create new opportunities for laboratorians. Some labs may view INR self-testing as competition, but in reality, lab testing remains an indispensable component of patient care. Further, lab testing for the inpatient population isn’t going away. For warfarin patients specifically, lab testing may be indicated if POC INR testing isn’t available, if self-testing or POC sample results are out of range, or if patients aren’t good candidates for self-testing for any reason.

The growth of self-testing for warfarin patients also provides an opportunity for laboratorians to think more broadly about ways to help their healthcare system identify the best options for patients. Allowing patients to self-test for INR at home can contribute to more streamlined laboratory workflows, better time management for laboratorians, and an increased ability to focus on higher-value tasks.6

As labs continue to look at ways to enhance their value within organizations and meet patient and provider needs, institutions that also take into consideration the option for self-testing hold the potential to provide increased patient satisfaction and innovative testing solutions that can support community and telehealth patient-care models. Laboratorians can communicate information regarding sample integrity challenges when clinics are located far away from the central lab, correlation data between POC and lab INR results, and differences among the various methods. This allows laboratorians the opportunity to step into a consultative role, helping to demonstrate their value as a knowledgeable resource for INR testing options.

For example, some warfarin patients who live in rural areas and depend on a lab or POC provider for their INR testing may not have ready access to another outlet if the clinic they regularly visit closes. Laboratorians are ideally poised to communicate about each INR testing option with healthcare providers, who in turn can share the information with their patients to decide on the best course of action. The National Blood Clot Alliance web site ( is an excellent patient resource for information about self-testing options for warfarin patients.

The future of oral anticoagulant self-testing

Today, self-testing is only performed in approximately five percent of U.S. patients treated with warfarin. The option is much more widely used in Europe, primarily in Germany and Italy where 25 percent and 20 percent of warfarin patients, respectively, are currently self-testing to monitor their INR. The difference may lie in the fact that a number of U.S. providers may be unaware that patient self-testing is an option for their warfarin patients.

Recent technology advances, such as handheld INR self-testing meters that incorporate Bluetooth technology, could lead to more interest in self-testing. Laboratorians play a vital role in helping clinicians deliver the best patient care possible. There is a large population of patients who will continue to rely on warfarin therapy, and laboratorians can demonstrate their value by collaborating with providers to identify the best testing options for patients.


  1. World Health Organization. WHO Model List of Essential Medicines.
  2. IMS Script Data 2018. Roche Data on File.
  3. National Blood Clot Alliance.
  4. Matchar DB, Jacobson A, Dolor R, et al. Effect of home testing of international normalized ratio on clinical events. NEJM. 2010;363.(17):1608-1620.
  5. Hospodar AR, Smith KJ, Zhang Y, Hernandez I. Comparing the cost effectiveness of non-vitamin K antagonist oral anticoagulants with well-managed warfarin for stroke prevention in atrial fibrillation patients at high risk of bleeding. Am J Cardiovasc Drugs. 2018 May 9. doi: 10.1007/s40256-018-0279-y.
  6. Wurster M, Doran T. Anticoagulation management: a new approach. Dis Manag. 2006;9(4):201-9.