Economic Aspects of Evaluation - Evaluation Methods in Biomedical Informatics - page 325

difference in effects) would estimate an ICER of around $9,700/year of life
gained.
Although the best case/worst case scenario is a common method for pre-
senting the variability in results, it is crucially dependent on the accuracy of
the estimates of the high and low values for component costs and effects.
One-Way Sensitivity Analysis
Although the best-case/worst-case method provides an estimate of the
spread of possible results from an overall analysis, it does not provide an
estimate of the effect of individual variables on the ICER. One-way sensi-
tivity analysis examines the effect of a single variable on the outcome. This
is calculated by varying the values of that single variable while holding all
others constant, and examining the effect on the ICER implied by changes
in that one variable. A simple one-way sensitivity analysis is shown in Figure
11.6, in which the hospital costs portion of strategy B in the example in
Figures 11.4 and 11.5 is systematically varied from $100,000 to $200,000
while all of the other costs and benefits are held constant at their baseline
values. The resulting graph indicates the effect of changes in that one
parameter (hospital costs in strategy B) on the outcome measure, the
ICER. It is common practice to conduct multiple one-way sensitivity analy-
ses to check the effect of all the primary variables in a cost model and
FIGURE 11.6. One-way sensitivity analysis. The x-axis represents the values of the
hospital costs component for strategy B of the cost analysis example shown in
Figures 11.5 and 11.6, the y-axis depicts the incremental cost effectiveness ratio
(ICER) implied by those values of hospital costs, holding all other costs and ben-
efits constant. As the costs of strategy B increase, the ICER worsens.