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, ventricular assist device, chronic atrial fibrillation, deep venous thrombosis, pulmonary embolism, venous embolism and thrombosis of deep vessels of lower extremity, or hypercoagulable states (e.g., antithrombin III deficiency, Factor V Leiden, protein C deficiency, and protein S deficiency, etc) when both of the following criteria are met:

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

Aetna considers prothrombin time home testing units experimental and investigational for all other indications (e.g., arterial embolism to the eye, atrial flutter, and Kawasaki disease) because its effectiveness for indications other than the ones listed above has not been established.

Aetna considers additional hardware/software systems needed for down-loading data from prothrombin time home testing units to computers for the management of anticoagulation as not medically necessary convenience items.

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 2 methods (r = 0.95), with 85 % of CoaguChek results within 0.5 INR units of the laboratory method.  On 4 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:

• Self-testing with the device should not occur more frequently than once a week; 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
• The patient must have been anticoagulated for at least 3 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.

Matchar and colleagues (2010) examined the effect of home testing of INR on clinical events in patients with atrial fibrillation or mechanical heart valves.  These investigators randomly assigned 2,922 patients who were taking warfarin because of mechanical heart valves or atrial fibrillation and who were competent in the use of point-of-care INR devices to either weekly self-testing at home or monthly high-quality testing in a clinic.  The primary end point was the time to a first major event (stroke, major bleeding episode, or death).  Patients were followed for 2.0 to 4.75 years, for a total of 8,730 patient-years of follow-up.  The time to the first primary event was not significantly longer in the self-testing group than in the clinic-testing group (hazard ratio, 0.88; 95 % confidence interval [CI]: 0.75 to 1.04; p = 0.14).  The 2 groups had similar rates of clinical outcomes except that the self-testing group reported more minor bleeding episodes.  Over the entire follow-up period, the self-testing group had a small but significant improvement in the percentage of time during which the INR was within the target range (absolute difference between groups, 3.8 percentage points; p < 0.001).  At 2 years of follow-up, the self-testing group also had a small but significant improvement in patient satisfaction with anti-coagulation therapy (p = 0.002) and quality of life (p < 0.001).  The authors concluded that as compared with monthly high-quality clinic testing, weekly self-testing did not delay the time to a first stroke, major bleeding episode, or death to the extent suggested by prior studies.  These results do not support the superiority of self-testing over clinic testing in reducing the risk of stroke, major bleeding episode, and death among patients taking warfarin therapy.

Bonaros et al (2004) stated that ventricular assist device (VAD) implantation is associated with impaired primary hemostasis and thromboembolic complications.  Recently, a new generation of implantable continuous flow axial pumps was introduced into clinical application.  To study the potential thrombogenic properties of this type of pump, these researchers applied extensive platelet monitoring.  In their institution, 13 patients received the MicroMed DeBakey VAD as a bridge to transplantation.  Routine coagulation tests (platelet count, activated partial thromboplastin time, prothrombin time, anti-thrombin III activity) and platelet function tests (whole blood aggregometry, thrombelastography, flow cytometry) were performed.  No clinically relevant thromboembolic events were detected.  No correlation was found between global function tests, platelet aggregation, and thrombelastography.  No correlation was detected between platelet activation and hemolysis parameters.  Platelet aggregation and coagulation index were significantly suppressed early after operation.  A subsequent phase of hyper-aggregability, starting around day 6, suggested the initiation of anti-aggregation therapy.  Platelet activation markers were up-regulated in the post-operative period but were returned to pre-operative levels after initiation of aspirin.  In contrast to routine coagulation monitoring, platelet function tests reflect in detail the coagulation status of blood pump recipients and the efficiency of anti-aggregation therapy.  Aspirin and dipyridamole therapy in addition to oral anti-coagulation using phenprocoumon may contribute to platelet function and clot mechanics restoration and is, therefore, recommended for patients after VAD implantation.

Joshi and colleagues (2007) noted that prothrombin time, expressed as INR and activated partial thromboplastin time (aPTT), are standard methods of monitoring coumadin and heparin administration.  Prothrombin activation fragment (F1.2) is an index of in vivo thrombin generation.  These investigators hypothesized that F1.2 would provide a better surrogate of thromboembolism risk than standard coagulation assays during VAD support.  In this study, INR, PTT and F1.2 were analyzed in 31 patients after implantation of a left-sided VAD daily during hospitalization and weekly after discharge.  Thromboembolic events (TE) were defined by evidence of neurological injury revealed by plasma levels of S-100beta.  The relationships between F1.2, INR for patients on coumadin and aPTT for patients on heparin were evaluated from 1,250 observations of blood samples.  S-100beta was positively correlated with F1.2, but not with INR and aPTT.  Correlation between S-100beta and F1.2 is significantly higher than with the other 2 markers (p < 0.0001).  Higher values of aPTT and INR were not associated with TE.  Compared to conventional coagulation assays, the F1.2 level provides a single endpoint that is a more accurate predictor of TE after VAD implantation.  The authors stated that further trials that incorporate the F1.2 marker into anti-coagulation algorithms may help reduce adverse events in this high-risk population.