Economic evaluation alongside factorial trials: a systematic review of empirical studies

Abstract

Although economic evaluations have been performed alongside factorial trials, there seems to be limited guidance/consensus on appropriate methods of analysis. Following Centre for Review and Dissemination guidance, a systematic review of published literature for all years was performed to explore how economic evaluation alongside factorial trials have been conducted and only full economic evaluations conducted alongside factorial trials were included. A total of 16 relevant studies were identified, and an assessment of these indicated that two methods: within-the-table and at-the-margins approaches were used for the analysis. With the exception of one study, all others did not consider interactions in costs and outcomes or give a detailed explanation of why a particular approach was adopted. The authors recommend that additional guidance is needed, and further research is required to evaluate the impact of alternative methods on policy recommendations and establish good practice methods for the economic analysis of factorial trials.

Keywords:

• cost-benefit analysis
• cost–effectiveness
• cost-utility analysis
• economic evaluation
• factorial design
• factorial trial

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• There is a growing interest by health economists in using factorial trials when analyzing economic data in trial-based economic evaluations. However, methods for the economic analysis of factorial trials remain unclear and there seems to be limited guidance on which method is the most appropriate and under which circumstances.

• The results from this study showed that two different methods: ‘within-the-table’ and ‘at-the-margins’ approaches were used for the analysis. However, with the exception of one study, all others did not consider interactions in costs and outcomes or give a detailed explanation of why a particular approach was adopted.

• This review found that although there was consistency in the application of general principles for conducting economic evaluations, there was lack of agreement with respect to methods for the economic analysis of factorial trials.

• Further research is required to evaluate the impact of alternative methods on policy recommendations and establish good practice methods on the design and economic analysis of factorial trials.