title: What happens to value of information measures as the number of decision options increases?
abstract: OBJECTIVE
  To explore what happens to the expected value of perfect information (EVPI) as an increasingly large number of decision options is considered.
  
  
  METHODS
  A stylised model of screening for a hypothetical cancer. The model was used to test different possible ages for 'once in a lifetime' screening under a variety of assumptions about model parameter uncertainty. Initial model runs only considered screening at ages which are multiples of 16 years, then multiples of 8 years were allowed, then 4 years, etc.
  
  
  RESULTS
  Effects of more refined choice sets on the cost-effectiveness acceptability frontier (CEAF) and EVPI are shown. The CEAF collapses to zero for threshold incremental cost-effectiveness ratios at which screening at some age is preferred to no screening, while the EVPI stabilises at a non-zero figure.
  
  
  CONCLUSIONS
  The CEAF is likely to be highly dependent on the choice of options when these are a selection from a very large set of possible options. In contrast, the EVPI can be reasonably approximated by a model with a slightly limited choice set.
authors: Health Economics Unit, University of Birmingham, Birmingham, UK. p.m.barton@bham.ac.uk
authors: Pelham
authors: P
authors: Barton
mesh_terms: D000367:Age Factors; D001499:Bayes Theorem; D002755:Choice Behavior; D003362:Cost-Benefit Analysis; D003661:Decision Support Techniques; D055088:Early Detection of Cancer / Q000191:economics*; D006801:Humans; D033181:Information Dissemination; D008962:Models, Theoretical; D019057:Quality-Adjusted Life Years