A survey of core outcome set developers

Background A systematic review of core outcome sets (COS) identified 250 reports relating to 198 studies [1]. The review showed that a range of methods have been used, in a variety of ways, to develop core outcome sets. Furthermore, we found that of the 178 studies that described the methods they used to determine the core outcome set, 164 (92%) did not provide an explanation regarding their choice of methodology. To our knowledge, there is little guidance about how to conduct or report COS studies and it is currently uncertain which of these methods are the most suitable, feasible and efficient. It is important to investigate COS developers’ choice of approach as this is a new area of research, and in order to formulate guidance in this area we need to try and understand the current situation, including the influences of methodological choices being made.