Telephone-Based INR Management

Home monitoring of blood pressure and blood glucose have become mainstays in the treatment of hypertension and diabetes, allowing patients to take an active role in their disease management. These home-monitoring results can also be valuable to clinicians and more frequent monitoring has been associated with improved disease control. 

Similarly, people taking warfarin often ask if they can monitor their international normalized ratio (INR) from home, largely to alleviate the burden of frequent trips to clinic. While home INR monitoring poses unique challenges that may limit its widespread use in a community-dwelling population, it may be useful for the right patients.

Choosing the Right Patient

As with any therapy, patient assessment and the subsequent evaluation of potential risks and benefits is essential. Patients better suited for home monitoring are more likely to be those receiving stable doses of warfarin and attaining consistently therapeutic INR values. Although the availability of frequent testing may be desirable in patients with unstable INR values to allow for more frequent INR assessment and dose titration, in-clinic, one-on-one counseling and education is likely too important to replace with telephone-based counseling in these cases. 

Specific patient factors—eg, comorbidities, location, and transportation issues—may influence the decision to start home-based INR management. However, each case should be evaluated individually. 

Safety

Safety considerations are a big concern of home monitoring. For example, if patients test themselves and record very high INR values and/or are experiencing any signs or symptoms of bleeding regardless of the INR value, immediate physician evaluation, assessment, and plan development is not possible. Assessment over the telephone relies on patients to accurately describe and characterize their symptoms, which is not as reliable as physician assessment. Patients will most likely be asked to come to clinic, but presentation will not be immediate and delays in presentation to clinic may lead to negative outcomes. 

That said, if elevated INR (or subtherapeutic) values are recorded, close INR monitoring is likely easier to attain with home monitoring—potentially improving safety. Close monitoring can also be used to ensure that therapeutic values are maintained when a change in medication may impact the INR, again improving safety. However, these situations are likely temporary and the more frequent monitoring likely will not continue indefinitely. 

Remember to counsel patients against self-adjusting their dosing regimen based on INR results without the supervision and recommendation of a physician. Patient–physician communication is vital to ensure safety is not compromised.

Efficacy 

A recent study found that home INR monitoring improved the time in the therapeutic range (TTR) compared to monthly clinic visits, due to more frequent monitoring (eg, twice weekly at home vs monthly in-clinic assessments).¹ As previously discussed (see When Can Intervals Between INR Checks Be Extended?, November 2014, page 865-866), some stable patients can extend the interval between INR checks for up to 12 weeks to alleviate the burden associated with monthly clinic visits. 

Home INR monitoring may serve as a way to still obtain monthly INR values in between these clinic visits. This compromise may satisfy both patients who want to reduce their number of in-clinic visits and physicians who want to ensure safe and efficacious use of warfarin via monthly (or more frequent) INR checks. Home INR monitoring can therefore improve INR values (making physicians happy) and limit the number of trips to the clinic (making patients happy).

Billing and Cost 

Unlike home blood pressure monitoring which only requires an initial investment for the monitor, home INR monitoring is more analogous to home blood glucose monitoring that requires both the initial purchase of the monitor plus reoccurring charges for test strips. Strips for INR monitoring are considerably more expensive than blood glucose strips and may cost up to $5. 

Insurance coverage for home INR monitoring supplies is possible, but not universally available with all plans. However, some patients may justify these out-of-pocket costs as less expensive than the time and travel required for an in-clinic assessment.

From a physician perspective, reimbursement for telephone-based monitoring of INR is not always guaranteed. New changes in Medicare billing in 2015 may allow for reimbursement of chronic disease state management, potentially covering INR monitoring. Furthermore, the physician still incurs the liability associated with home INR monitoring. 

Before considering home monitoring, the patient should first determine if insurance will cover the cost of home monitoring testing supplies. After assessing the financial commitment, patients may elect to continue with in-clinic monitoring only, thus negating the need for further consideration and evaluation.

However, if home monitoring is the next step, a reliable method of communication should be established. Next, develop a protocol to determine when the home INR checks will be completed, how and when the results will be sent to the physician’s office, and who will contact the patient from the office. 

Specific INR values (eg, >7) or reported signs/symptoms of bleeding should automatically trigger in-clinic visits for physician evaluation and assessment. If the patients are unwilling to come to clinic in these situations, home monitoring should not be pursued. 

Finally, outline a treatment plan for in-clinic visits (eg, every 3 months) in addition to home monitoring. In-clinic assessment, counseling, and education should not be completely abandoned due to the availability of home monitoring.

The Take-AWAY:

1. Home monitoring may allow for increased TTR due to more frequent monitoring, and improved patient satisfaction due to fewer in-clinic assessments.

2. The inability to immediately assess the patient for out-of-range INR values or signs/symptoms of bleeding is not available with home INR monitoring. The patient should agree to immediately follow-up in-clinic in these situations.

3. Currently, physician reimbursement for telephone-based INR monitoring is not universal to all insurance plans. Changes to Medicare in 2015 may allow for better reimbursement, so as to offset the incurred liability and time commitment of managing home INR values. ν

Eric A. Dietrich, PharmD, BCPS, graduated from UF College of Pharmacy in 2011 and completed a 2-year fellowship in family medicine where he was in charge of a coumadin clinic. He now works for the UF Colleges of Pharmacy and Medicine. 

Reference:

1. Matchar DB, Love SR, Jacobson AK, et al. The impact of frequency of patient self-testing of prothrombin time on time in target range within VA Cooperative Study #481: The Home INR Study (THINRS), a randomized, controlled trial. J Thromb Thrombolysis. 2014 Sep 11 [Epub ahead of print]