Objectives: This article provides a detailed understanding of the differences in selected formulary submission guidelines supplied by various health technology assessment (HTA) agencies and indicates how these differences can impact the evidence base used to populate the HTA.

Methods: Detailed summaries of the recommended methods for evidence generation, organized by topic areas relevant for clinical and economic data, for twelve countries in Europe, North America, and Australia where HTA processes are well developed were prepared. Using these summaries, we provide examples of the likely impact these differences in recommended methods could have on the evidence base used to evaluate new health technologies.

Results: Areas where recommendations differed included methodologies for systematic literature reviews (e.g., preferred databases and study designs for inclusion); selection of appropriate comparators; guidance on critical appraisal and synthesis of clinical evidence; appropriate sources for health value measures, resource use, and cost data; and approaches to uncertainty analyses. Performing literature searches that capture all relevant studies and then creating subsets of the literature based on a listing of country-specific requirements could allow for direct comparison of the evidence bases associated with the different guidelines.

Conclusions: If the formulary submission guidelines were followed as written, different (although overlapping) bodies of evidence likely would be generated for each country, which could contribute to disparate assessments and recommendations. This comparison of the formulary submission guidelines could contribute to an understanding of why clinical and reimbursement decisions vary across countries.