Reviewing the evidence to inform the population of cost-effectiveness models within health technology assessments.

Health technology assessments (HTA) typically require the development of a cost- effectiveness model which necessitates the collection of information, in addition to clinical effectiveness evidence, to populate the model parameters. The reviewing activity associated with model development should be transparent and reproducible but can result in a tension between being both timely and systematic. Little procedural guidance exists in this area. The purpose of this paper is to provide guidance, informed by focus groups on what might constitute a systematic and transparent approach to reviewing information to populate model parameters where little procedural guidance exists.