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Which approach to anticoagulation management is best? Illustration of an interactive mathematical model to support
Gregory P Samsa1, David B Matchar, David L Phillips
1Center for Clinical Health Policy Research, Duke University Medical Center, Durham, NC, USA. samsa001@mc.duke.edu
Background:
Among patients with atrial fibrillation or mechanical heart valves, determining the best approach to oral anticoagulation largely depends on comparing the costs of anticoagulation management with the costs of events (thromboembolism and bleeding) averted. The Anticoagulation Management Event/Cost Model (ACME) is an interactive mathematical model intended to help clarify these trade-offs.
Methods:
The ACME is a series of linked, nested spreadsheets. At the least detailed level, the user specifies the percentage of patients falling into various management strategies (no anticoagulation, usual physician care, anticoagulation service, patient self-testing/self-management), and the ACME estimates event rates and costs. At more detailed levels the ACME performs a series of weighted average calculations combining, for example, utilization times unit price. Cost categories are divided into event-related and management-related costs (costs of management, testing, and medication).
Results:
Regardless of how anticoagulation is subsequently managed, perhaps the greatest benefit is obtained by moving patients who are not currently receiving anticoagulation onto warfarin. Additional benefits can be obtained by eliminating outliers (extremely high or extremely low anticoagulation levels). If changing to a more intensive approach also serves to reduce the tendency for physicians to prescribe anticoagulate below the optimal range, additional savings can be anticipated. The cost calculation typically involves a trade-off between increased up-front costs of anticoagulation management versus greater down-line savings associated with a decreased number of events. To assess the quality of anticoagulation within a given organization, it is critical to know the distribution of clotting levels for the population under anticoagulation.
Conclusions:
Interactive mathematical models, if sufficiently well documented, can be helpful in clarifying decisions regarding costs and benefits of various methods of anticoagulation.