Aetna considers prothrombin time home testing units (home INR testing) medically necessary durable medical equipment for persons who require chronic oral anticoagulation with warfarin for a mechanical heart valve, chronic atrial fibrillation, deep venous thrombosis, or venous embolism and thrombosis of deep vessels of lower extremity, where both of the following criteria are met:

1. The person must have been anticoagulated for at least 3 months prior to use of the home INR devices; and
2. The expected need for home INR testing is 6 or more months.

Aetna considers prothrombin time home testing units experimental and investigational for all other indications.

This policy is consistent with the conclusions of an assessment from the Centers for Medicare & Medicaid Services (CMS, 2008).

Prothrombin time home testing systems are portable, battery-operated instruments for the quantitative determination of prothrombin time from finger-stick whole blood. These products are designed to aid in the management of high-risk patients taking oral anticoagulants. They require considerable patient training and compliance to be useful. Self-testing and/or self-management by the patient using home international normalization ratio (INR) monitors represent another model of care with the potential for improved outcomes as well as greater convenience. Self-testing may provide a convenient opportunity for increased frequency of testing when deemed necessary. The use of the same instrument may increase the degree of consistency in instrumentation, and self-testing provides the potential for greater knowledge and awareness of therapy which may lead to improved compliance. There is, however, insufficient evidence comparing the effectiveness of patient self-testing and self-management using a home INR monitor to care provided by an anticoagulation management service. Ansell, et al. (2001) explained: "Although a growing number of studies indicate the superiority of patient PST [patient self-testing] or PSM [patient self-management of dose adjustments] over UC [usual care, i.e., patients managed by their usual physicians], there is little evidence comparing them to care provided by an AMS [anticoagulation management service (i.e., anticoagulation clinic)]. PST and PSM require special patient training to implement, and therapy should be managed by a knowledgeable provider. A definitive recommendation cannot yet be made as to the overall value of PST or PSM."

In a randomized controlled trial, Gardiner and colleagues (2005) ascertained if patients can achieve accurate INR values through patient self testing (PST) by means of the CoaguChek S (Roche Diagnostics, Lewes, UK). The main outcome measurements were comparability of INR values obtained by PST and the hospital laboratory, patient acceptability as assessed by a questionnaire and anticoagulant control. A total of 84 subjects (53 men, 31 women; median age of 59 years), receiving long-term oral anticoagulation (warfarin), were recruited. Subjects were randomized to weekly self-testing or continuing 4-weekly hospital laboratory monitoring of INR. Comparison of INRs (n = 234) showed no significant differences between the CoaguChek (median INR 3.02) and laboratory testing (median INR 3.07). There was excellent correlation between the two methods (r = 0.95), with 85% of CoaguChek results within 0.5 INR units of the laboratory method. On four occasions, differences of greater than 1 unit INR were obtained, but in each case the patient's anticoagulation was unstable (INR greater than 4.5 by both methods) and the differences in INR would not have altered patient management. The results showed that 87% of patients found self-testing straightforward, 87% were confident in the result they obtained and 77% preferred self-testing. These investigators concluded that PST is a reliable alternative to hospital clinic attendance and is acceptable to the majority of suitably trained patients.

In 2002, CMS issued a national coverage determination for the use of home prothrombin time INR monitoring for anticoagulation management for patients with mechanical heart valves on warfarin. More recently, a CMS Decision Memorandum (2008) concluded that there is sufficient evidence of the effectiveness of home prothrombin time (INR) monitoring for patients with a mechanical heart valve, chronic atrial fibrillation, or deep venous thrombosis. The monitor and the home testing must be prescribed by a treating physician and the following requirements must be met:

• The patient must have been anticoagulated for at least three months prior to use of the home INR devices; and
• The patient must undergo an educational program on anticoagulation management and demonstrated the correct use of the device prior to its use in the home; and
• The patient continues to correctly use the device in the context of the management of the anticoagualtion therapy following initiation of home monitoring; and
• Self-testing with the device should not occur more frequently than once a week.