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

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.