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Purpose: Value of information analysis provides a framework for the analysis of uncertainty within economic analysis, by focussing on the value of obtaining further information to reduce uncertainty. The mathematical definition of the expected value of perfect information (EVPI) is fixed though there are different methods in the literature for its estimation. In this study these methods are explored and compared. Methods: Analysis was conducting using a disease model for Parkinson’s disease. Five methods for estimating partial EVPIs (EVPPIs) were used: a single Monte Carlo simulation (MCS) method, the unit normal loss integral (UNLI) method, a two stage method using MCS, a two stage method using MCS and quadrature and a difference method requiring two MCS. The single MCS method is appropriate only when the complement of the data set is multi linear in net benefit, the UNLI method is appropriate when data parameters are linear in net benefit and are normally distributed. The other three methods are general methods in that they are argued to be appropriate for all data parameters. EVPPI was estimated for each individual parameter in the model as well as for three groups of parameters (transition probabilities, costs and utilities). In each case, EVPPI was estimated by the three general methods and either of the other methods if appropriate. Analysis compared estimates of EVPPI based on alternate numbers of replications as well as the complexity of analysis required for estimation. Results: Using 5000 replications, four methods returned similar results for EVPPIs. With 5 million replications, results were near identical. However, the difference method repeatedly gave estimates substantially different to the other methods. The single MCS and UNLI methods were the least complex methods to use but are restricted in their appropriateness. The two stage MCS and quadrature based methods are complex and time consuming. Conclusions: The difference method is not rooted in the mathematical definition of EVPI and is clearly an inappropriate method for estimating EVPPI. Thus, where appropriate EVPPI should be estimated using either the single MCS or UNLI method. However, as often in cases where neither of these methods is appropriate, the two stage MCS and quadrature methods should be used.
See more of Poster Session - Public Health; Methodological Advances
See more of The 26th Annual Meeting of the Society for Medical Decision Making (October 17-20, 2004)