Guidance for protocol content and reporting of factorial randomised trials: explanation and elaboration of the CONSORT 2010 and SPIRIT 2013 extensions

This report presents the explanation and elaboration paper for the CONSORT (Consolidated Standards of Reporting Trials) 2010 and SPIRIT (Standard Protocol Items: Recommendations for Interventional Trials) 2013 extensions for factorial trials. Factorial trials involve randomising participants to more than one intervention, often with the aim of evaluating multiple interventions in one study or assessing whether treatments interact. The CONSORT and SPIRIT statements have been extended to allow for the unique features of the factorial design. Reporting items along with detailed explanations and examples of good practice are provided, as well as a glossary of key terms and an overview of the methodological features of factorial trials.