Transparent and complete reporting of surrogate endpoints in trials: the SPIRIT-Surrogate and CONSORT-Surrogate extensions

The adoption and adherence to clinical trial reporting guidelines is a key intervention to reduce research waste, as highlighted a decade ago in The Lancet's Research: Increasing Value, Reducing Waste Series.1 Inadequate reporting of research is arguably the easiest to fix in the context of research waste.2 Randomised trials are resource-intensive studies that provide robust evidence for evaluating the effectiveness of interventions. Two reporting guidelines have improved the reporting of trials over the years: SPIRIT (Standard Protocol Items: Recommendations for Interventional Trials) for trial protocols and CONSORT (Consolidated Standards of Reporting Trials) for trial reports.2 However, these guidelines are not always sufficient for adequate reporting of all types of trials, such as those using surrogate endpoints as primary outcomes.