Importance and relevance of this study
There is a relatively low uptake of COSs by trialists [Our findings show that compared to a MRD, a commonly-used approach in COS development [Advantages of using the RTD method include reduced time to complete the survey overall, as the RTD was live for 14 weeks compared to the MRD being live for 20 weeks.Additionally, the RTD achieved better convergence on outcome ratings. As many COSs were developed five or more years ago (see COMET database: 