SPIRIT 2025 explanation and elaboration: updated guideline for protocols of randomised trials

High quality protocols facilitate proper planning, conduct, reporting, and external review of randomised trials, yet their completeness varies and key elements are often not considered. To strengthen good reporting of trial protocols, the SPIRIT (Standard Protocol Items: Recommendations for Interventional Trials) 2013 statement has been updated to incorporate new evidence and emerging perspectives. This SPIRIT 2025 explanation and elaboration document provides users with exemplars of reporting in contemporary trial protocols, contextual elaboration, more detailed guidance on reporting, references to key empirical studies, an expanded checklist, and a link to a website for further information. The document is intended to be used in conjunction with the SPIRIT 2025 statement and serves as a resource for researchers planning a trial and for others interested in trial protocols.