Ansell.qxp 29/7/08 10:08 Page 22
Cardiac Monitoring
International Normalized Range Monitoring for Anticoagulated Patients at Home
a report by
Debra Green, MD,
1
Jack Ansell, MD
1
and Stephan Moll, MD
2
1. Department of Medicine, Lenox Hill Hospital, New York; 2. University of North Carolina School of Medicine, Chapel Hill
Oral anticoagulants are one of the most common causes of drug-induced versus PSM trials and the control groups were UC or ACC care. In a large
adverse events.
1
Expert dose management, which keeps the patient within randomized study, Beyth et al.
27
compared PST with UC management. The PST
a narrow therapeutic international normalized range (INR), is required to group had a 5.6% incidence of major hemorrhage compared with a 12%
avoid adverse events and optimize therapy. Anticoagulation clinic (ACC) incidence in the UC group (p=0.049). Venous thrombosis occurred at a rate
management has been shown to improve outcomes compared with the of 8.6% in the PST group compared with 13% in the UC group, but the
routine management provided by physicians,
2
but estimates suggest that difference was not significant. In a number of trials comparing PSM with UC,
fewer than 50% of patients in the US on oral anticoagulants are managed mean TTR for the PSM arms was 73% versus 59.9% for the UC arms.
28,34–36,38–41
by such clinics. Point-of-care (POC) prothrombin time monitoring None of these trials showed differences in major hemorrhage or thrombosis,
technology, developed 20 years ago, introduced a new model of care by although none of them were powered to do so. When one assesses the
allowing for fingerstick INR monitoring and patient self-testing (PST). outcomes of PST compared with management by an AC, the TTR is only
Under this model, patients may either monitor their own INR at home and minimally improved (73.3 and 67.1%, respectively).
32,33,38
The same is found
receive dose-adjustment guidelines from their physician, or actually adjust when PSM is compared with AC care (71.4 and 66.6%, respectively).
29,30,37
their own anticoagulation dose after proper training.
2
Numerous Only one trial found a significant difference in the rate of major bleeding and
published clinical studies conducted during the past 10 years have thromboembolism.
30
These studies and others have been the subject of several
validated the benefits and value of POC testing for anticoagulation detailed meta-analyses.
42,43
These meta-analyses are somewhat problematic in
monitoring compared with venous blood draws and laboratory testing. that some combine results from PSM and PST, while in others the controls are
Despite the clinical evidence, many healthcare professionals have been a combination of UC and ACC management. In the most comprehensive
reluctant to incorporate POC testing into their practices. There are several meta-analysis to date, Heneghan et al. pooled estimates from 14 randomized
devices available for self-testing that rely on capillary whole blood and are trials of PST showing a significant reduction in thromboembolic events (odds
lightweight, portable, easy-to-use, accurate, and precise (see Table 1). INR ratio [OR] 0.45, 95% confidence interval [CI] 0.30–0.68), all-cause mortality
results from these portable devices have been shown to equal those from (OR 0.61, 95% CI 0.38–0.98), and major hemorrhage (OR 0.65, 95% CI
phlebotomy plasma INRs determined in a central laboratory.
3
0.42–0.99) versus the comparator.
42
For PST and PSM combined, there were
significant reductions in thromboembolic events (OR 0.27, 95% CI 0.12–0.59)
Patient Self-testing/Patient Self-management and death (OR 0.37, 95% CI 0.16–0.85), but not major hemorrhage (OR 0.93,
Many studies
4–28
have reported on the accuracy and precision of POC 95% CI 0.42–2.05). Both PST and PSM studies are included.
instruments when used by patients to obtain an INR, and on the
suitability of POC instruments for monitoring anticoagulant therapy. Based on these data, portable PT monitors offer the potential to lower the
Limitations to their accuracy and precision include greater differences risk–benefit ratio of anticoagulant therapy, improve patient satisfaction and
compared with a standard plasma-based methodology as INRs increase possibly patient compliance, and, by reducing the labor intensity of
above the therapeutic range,
6,26
incorrect calibration of the international physician management, encourage the use of warfarin when indicated.
sensitivity index (ISI) of the POC instruments,
6
the inability to calculate a Although larger randomized, prospective trials are needed, current data
mean normal prothrombin time (PT),
27
and inaccuracies in INR suggest that future management of anticoagulation should include PST and
determination in patients with antiphospholipid antibodies. Multiple PSM therapy. This fact was recognized by the most recent American College
studies focusing on clinical outcomes and patient satisfaction have of Chest Physicians (ACCP) Consensus Conference on Antithrombotic
determined the suitability of PST. It is important to note the comparator Therapy, where the following recommendation was made: “PSM is a choice
group used in controlled trials, since this influences differences. When a made by patients and healthcare providers that depends on many factors.
usual care (UC) model of anticoagulation management is the comparator In patients who are suitably selected and trained, PST or PSM is an effective
group, the PST or patient self-management (PSM) arms will often show alternative treatment model. We suggest that such therapeutic
marked improvement in time in therapeutic range (TTR, a surrogate management be implemented where suitable (Grade 2B).“
2
measure of quality) or in efficacy and safety outcomes. Alternatively, when
PST or PSM is compared with a control arm managed by an ACC, the Patient Education
differences are minimal. Table 2 summarizes randomized trials in which 50 or While generalized training guidelines for PSM of any disease state apply to
more patients were studied and clinical outcomes were reported as TTR, self-anticoagulation, the high risk–benefit ratio of warfarin and the potentially
adverse events, or both.
27–37
Studies were stratified by whether they were PST serious consequences of non-therapeutic levels of anticoagulation warrant
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