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Original Studies |
Sections of Neurosurgery (J.T.K.), General Internal Medicine
(A.C.J.), and Endocrinology (D.C.A.), Department of Veterans Affairs
Medical Center; and the Department of Neurosurgery (J.T.K.); the
Program in Health Care Research (J.T.K., A.C.J., D.C.A.); the Division
of General Internal Medicine, Department of Medicine (A.C.J., D.C.A.);
the Division of Clinical and Molecular Endocrinology, Department of
Medicine (D.C.A.), Case Western Reserve University and University
Hospitals, Cleveland, Ohio 44106
Decision analysis: A
systematic and quantitative approach to decision making under
conditions of uncertainty. The probabilities of each possible event and
the consequences of those events, given various conditions and
assumptions, are stated explicitly. A mathematical model of a problem
and its possible treatments, incorporating options, probabilities, and
outcomes, is used to calculate the "best" decision.
"Best" is
determined based on expected values, the calculated average outcomes
from the branches of the decision tree.
Decision
tree: A flow chart of a decision and its probabilistic
consequences. The initial choice and outcomes are graphically
represented in branches of the tree. These branching points are either
chance nodes that have biologically determined outcomes or decision
nodes (usually only one) in which the outcomes are decided by choice of
the physician or patient.
Discount rate: The rate
used to compute the present value of a clinical or monetary events that
occur in the future (typically 5ü.
Health-related
quality of life: As a construct, health-related quality of life
(HRQOL) refers to the impact of the health aspects of an individual’s
life on that person’s quality of life or overall well-being; also used
to refer to the value of a health state to an individual.
Incremental cost: The cost of one alternative minus
the cost of another.
Incremental QALY: The number
of QALY of one alternative minus the number of QUALY of another.
Incremental cost/QALY: The cost of one alternative
minus the cost of another for one additional QALY.
Incremental cost-effectiveness (ratio): The ratio of
the difference in costs between two alternatives to the difference in
effectiveness between the same two alternatives.
Marginal benefit: The added benefit generated by the
next unit consumed.
Marginal cost: The added cost
of producing one additional unit of output.
Markov
model: A type of mathematical model containing a finite number of
mutually exclusive and exhaustive health states. During each time
period of uniform length, patients can move from one state to another
based on probability rules.
Present value: The
value to the decision maker now of outcomes occurring in the future. In
economic evaluations (present value analysis), future costs and
benefits are expressed in current dollars. Future costs and benefits
are multiplied by a discount factor to convert them to current dollars.
QALYs: A measure of health outcome that assigns to
each year a weight, ranging from 0–1, corresponding to the quality of
life during that year. By convention, perfect health is assigned a
value of 1.0, and death is assigned a value of 0.0. Total QALYs are
obtained by adding the product of the quality of life value and the
number of years in that state (e.g. quality of life
value = 0.7, yr = 10, QALYs = 0.7 x 10 =
7.0).
%Sensitivity analysis: A method to assess the
effects of key assumptions or values on the final result of a
mathematical model. The assumptions are varied over a range of values
to determine their effects on the result, i.e. a test of the
stability of the conclusions of an analysis over a range of probability
estimates, value judgments, and structural assumptions. Large
differences in effects indicate that the analysis is "sensitive"
to
the assumption. One-way sensitivity analysis varies one variable at a
time. Two-way sensitivity analysis varies two at a time,
etc.
Time horizon: The period of time
for which costs and effects are measured in a cost-effectiveness
analysis.
These definitions were derived and modified from
Refs. 73 and 74.
Address all correspondence and requests for reprints to: David C. Aron, M.D., M.S., Medical Service 111(W), Department of Veterans Affairs Medical Center, 10701 East Boulevard, Cleveland, Ohio 44106. E-mail: aron.david{at}cleveland.va.gov
The objective of this study was to compare the cost-effectiveness of four management strategies for a patient with an incidentally discovered asymptomatic pituitary microadenoma.
A decision analytic Markov model was used to determine the incremental cost-effectiveness of four clinical management strategies: 1) expectant management, 2) PRL screening, 3) an endocrine screening panel (PRL, insulin-like growth factor I, and 1-mg dexamethasone suppression test), and 4) magnetic resonance imaging (MRI) follow-up. The model incorporated the natural history of incidental microadenomas, test characteristics, pharmacological and surgical treatment outcomes, patient’s quality of life, discounting, and the costs of hormone testing, bromocriptine, MRIs, hospitalization for surgery, and physician services.
PRL screening, endocrine screening panel, and MRI follow-up all provided slightly greater quality-adjusted survival than expectant management, but the costs increased disproportionately more than the benefits. The incremental cost per quality-adjusted life year for PRL screening is $1,428, and that for the endocrine screening panel is $69,495. These results are most sensitive to patient anxiety about the microadenoma; increased anxiety shifts the recommended strategy to the endocrine screening panel.
We conclude that in patients with an incidental asymptomatic pituitary microadenoma, a single PRL test may be the most cost-effective management strategy.
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