Many nonrandomized retrospective studies have reported better outcomes in patients whose anticoagulant therapy is managed by an AMS vs management by a primary care physician or specialist alone.7 Compared with usual care, AMS programs have been shown to greatly improve patients’ TTR, thereby reducing hemorrhage or thrombosis as a consequence of excessive or subtherapeutic anticoagulation.4,20,21
Self-testing/self-management—which depends on adequate patient training—has similar benefits: Self-care facilitates more frequent monitoring and empowers patients, and may be a major factor in patient compliance.4 Individuals using their own portable INR monitors and managing their own care have been found to have improved TTRs and a lower frequency of major hemorrhage or thrombosis compared with patients receiving usual care.7,18 The recent THINRS trial randomized 2922 patients to perform weekly self-testing or receive monthly clinic-based testing at an institution with a system for providing anticoagulant care. The study confirmed that patient self-testing is feasible for most warfarin-treated individuals and that weekly home monitoring is as safe and effective as high-quality clinic-based testing.22
Who’s a candidate for self-management?
Various studies have found that, as with insulin-dependent diabetes, most patients who are independent and self-supporting are, in principle, capable of self-management of oral anticoagulation, regardless of education or social status.23,24 The only intellectual requirement is that the patient (or caregiver) grasp the concept of anticoagulant therapy and understand the potential risks. (For more help in determining whether your patient is eligible for self-management, see “Self-monitoring—for which patients?” on page 74.)
The patient must also be willing to actively participate in his or her own care and have sufficient manual dexterity and visual acuity. No previous experience in self-testing or monitoring is necessary.7
INR monitors for patients and physicians
Since the late 1980s, point-of-care devices that measure INR values have made it possible for an increasing number of patients to monitor the anticoagulant eff ects of warfarin without repeat visits to a health care facility. Of the 4 million US residents on warfarin, approximately 60,000 (1.6%) engage in self-testing, according to the International Self-Monitoring Association of Oral Anticoagulated Patients (www.ismaap.org).
One reason may be the cost. Portable monitors are available for approximately $2495, according to Alere Inc., a health management company—a price that may include supplies and training. The expense may not be covered by private insurers. However, in 2008, Medicare began covering the cost of INR monitors (and the testing materials required for their use) for seniors receiving anticoagulation therapy associated with mechanical heart valves, chronic atrial fibrillation, or venous thromboembolism.25 Portable monitoring devices include the following:
CoaguChek (http://www.coaguchek.com). The CoaguChek brand, now in its third generation, features both a monitor (CoaguChek XS) for patient use and a system (CoaguChek XS Plus) for health care professionals. CoaguChek has extended quality control and data management options.
INRatio2 PT/INR Monitor (www.hemosense.com). The HemoSense INRatio2 is a new whole-blood patient monitoring system. The device is well suited for use by both health care professionals and patients.
ProTime PT/INR Monitor (www.protimesystem.com). The ProTime Microcoagulation System is a portable, batteryoperated testing tool designed for both professionals and patients. There are also companies that sell or loan the devices to patients and provide the supplies, training, and support for enrollees engaged in self-testing, including Philips (http://www.inrselftest.com/content) and Roche (https://www.poc.roche.com/poc/home.do).
Preparing patients for self-management In addition to acquiring a monitor, patients interested in self-testing and management need to be aware that the risk of bleeding rises steeply when the INR exceeds 4.0—and the risk of thrombosis increases when INR values fall below 2.0.7
Guard against interactions. Emphasize that numerous environmental factors, such as drugs, diet, alcohol, and various disease states, can alter the pharmacokinetics of warfarin.26 Consequently, INR values need to be measured more frequently than the usual 4-week intervals when a patient taking warfarin adds (orstops taking) virtually any drug, dietary supplement, or herbal remedy, or significantly alters his or her vitamin K intake. Illnesses with a fever, such as infl uenza, or diarrhea and vomiting lasting more than one day, can also aff ect INR levels, and call for more frequent testing and possible adjustments in warfarin dosing.27
Explain that some drugs reduce warfarin’s anticoagulant eff ect by reducing its absorption or enhancing its clearance, while others—including many commonly used antibiotics—enhance the drug’s anticoagulant eff ect by inhibiting its clearance.6,7 Remind patients that the risk of bleeding is high when warfarin is combined with antiplatelet agents such as clopidogrel, aspirin, or nonsteroidal anti-infl ammatory drugs, among other medications.27 And caution them that excessive use of alcohol aff ects the metabolism of warfarin and can elevate the INR.26 (See Patient on warfarin? Steer clear of these drugs, in "Avoiding drug interactions: Here’s help," J Fam Pract. 2010; 59: 322-329.)