Pediatric Clinics of North America - CIPERJ

DECISION ANALYSIS IN PEDIATRIC HEMATOLOGY
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Fig. 2. Basic structure and components of a Markov model, using the example of a patient who
has DVT who can be treated with anticoagulant #1 or #2. Four possible Markov, or health,
states are included.
Usually, the exact probabilities cannot be estimated with certainty. Therefore,
the values that estimate the probabilities best are used in the original,
or base-case, analysis. In sensitivity analysis (discussed later), each probability
is varied over an estimated range. A rigorous literature search is performed
using a hierarchy of sources (case series / large cohort studies / prospective
randomized trials / systematic reviews), and the quality and applicability of
each source should be determined [10]. Probabilities must be assigned to each
branch emanating from a chance node, and for each chance node, the sum of
the probabilities must be equal to 1. In some cases there may be insufficient
data in the medical literature to inform every chance node in a decision
analysis model. Investigators then may turn to expert or personal opinion
to generate a probability estimate. Although these estimates certainly can
be rigorously tested later in sensitivity analysis, the need to use them does
decrease the validity of the technique.
Once the optimal strategy is identified in a decision analysis study, costs
can be added to the model to understand the cost-effectiveness or costutility
of that strategy compared with others. When performing a cost-effectiveness
analysis, an investigator should capture all health care use costs
and the productivity loss of patients’ caregivers [11]. It also is important
to differentiate cost data from charge data. Actual cost data always are preferred
in decision analysis models, as charge data can be arbitrary and often
depend highly on a third-party payer or treatment setting. A popular source
for medication costs is the Drug Topics Red Book, an annual reference reporting
the average wholesale price of prescription and over-the-counter
medications [12]. In the United States, Medicare and Medicaid reimbursement
data often are considered the best estimate of health care costs. Average
hospitalization costs can be derived from Medicare and Medicaid