A Synthesis of the Evidence: Safe and Effective Anticoagulation in the Outpatient Setting

Long-term anticoagulation with vitamin K antagonists (e.g., warfarin) has been shown to reduce major thromboembolic complications in patients with many common chronic conditions, including atrial fibrillation, history of deep vein thrombosis and pulmonary embolism, and mechanical heart valves. However, vitamin K antagonists have a very narrow therapeutic window requiring frequent laboratory monitoring to ensure that patients are neither excessively anti-coagulated, which increases the risk for bleeding, or under anti-coagulated, which increases the risk for thromboembolism. Since the management of long-term oral anticoagulation requires frequent testing and dose adjustment, anticoagulation clinics have been developed to streamline and standardize care.

Recently, investigators at the VA Evidence-Based Practice Center in Minneapolis conducted a literature review of articles published from 1997 through March, 2010 in order to answer three key questions regarding chronic anticoagulation therapy in the outpatient setting.

Question #1
For the management of long-term outpatient anticoagulation in adults, are specialized anticoagulation clinics more effective and safer than care in non-specialized clinics (e.g., primary care, physician offices)?

Answer: Evidence for the safety and efficacy of anticoagulation clinics is limited; however, overall it suggests that care provided within anticoagulation clinics may lead to better quality anticoagulation control as measured by time in therapeutic range. There is insufficient evidence to conclude that anticoagulation clinic care results in fewer deaths, thromboembolic events, or major bleeding events than care provided in usual care settings. Thus, there is insufficient evidence at this time to determine whether wider implementation of anticoagulation clinics within VA would improve major clinical outcomes.

Question #2
Is patient self-testing – either alone or in combination with patient self-management – more effective and safer than standard care delivered in either anticoagulation clinics or non-specialized clinics?

Answer: Compared to usual clinic care, patient self-testing, with or without self management, is associated with significantly fewer deaths and thromboembolic events without any increase in bleeding complications for a select group of motivated patients requiring long-term anticoagulation with Vitamin K antagonists. However, it should be noted that while the strength of the evidence was moderate for the thromboembolism and bleeding, it was low for mortality. Whether this care model is cost-effective and can be implemented successfully in the VA or other typical U.S. healthcare settings requires further study.

Question #3
What are the risk factors for serious bleeding in patients who are on chronic warfarin therapy?

Answer: Several factors have been shown to predict an increased risk of bleeding; for example, older age (over 75 years), first months following warfarin initiation, and comorbid conditions (e.g., diabetes). Risk indices (e.g., OBRI, HEMORR2HAGES) have been created by pooling together risk factors. These indices have been shown to stratify groups of patients into lower and higher risk groups based on the number and type of risk factors present. Either alone or in combination, these risk factors can likely be used to help clinicians and patients have a discussion about the risks of warfarin therapy.

Currently, there is not adequate evidence to suggest that any of the bleeding risk indices are meaningfully superior to the other indices. Future studies are needed to define the optimal use of risk factors or risk indices to reduce the risks of anti-coagulation.

This report is a product of the HSR&D Evidence-Based Synthesis Program (ESP), which was established to provide timely and accurate syntheses of targeted healthcare topics of particular importance to VA managers and policymakers–and to disseminate these reports throughout VA.

References:

Bloomfield H, Taylor B, Krause A, et al. Safe and Effective Anticoagulation in the Outpatient Setting: A Systematic Review of the Evidence. VA-ESP Project #09-009; 2011.

Bloomfield H, Krause A, Greer N, et al. Systematic Review and Meta-Analysis: Effect of Patient Self-Testing and Self-Management of Chronic Anticoagulation on Major Clinical Outcomes. Annals of Internal Medicine April 5, 2011;154(7):472-482.

Related editorial:

Anaya P and Moliterno D. Patient, Heal Thyself: The Ongoing Evaluation of Patient Self-Directed Care and Hand-Held Technology. Annals of Internal Medicine April 5, 2011;154(7):500-501.

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This Management eBrief is a product of the HSR&D Evidence Synthesis Program (ESP). ESP is currently soliciting review topics from the broader VA community. Nominations will be accepted electronically using the online Topic Submission Form. If your topic is selected for a synthesis, you will be contacted by an ESP Center to refine the questions and determine a timeline for the report.

This Management e-Brief is provided to inform you about recent HSR&D findings that may be of interest. The views expressed in this article are those of the authors and do not necessarily reflect the position or policy of the Department of Veterans Affairs. If you have any questions or comments about this Brief, please email CIDER. The Center for Information Dissemination and Education Resources (CIDER) is a VA HSR&D Resource Center charged with disseminating important HSR&D findings and information to policy makers, managers, clinicians, and researchers working to improve the health and care of Veterans.

This report is a product of the HSR&D Evidence-Based Synthesis Program (ESP), which was established to provide timely and accurate synthesis of targeted healthcare topics of particular importance to VA managers and policymakers - and to disseminate these reports throughout VA.

See the full reports online.