Grey literature

Clinical trial registers are databases that store information about ongoing and completed clinical trials. The purpose of these registers is to provide a comprehensive, public, and easily accessible source of information about clinical trials to increase transparency, reduce the risk of selective reporting, and allow stakeholders such as researchers, patients, and regulators to easily access and evaluate the available evidence. Clinical trial registers typically contain information such as the study design, inclusion and exclusion criteria, study location, and contact information for the study sponsor and principal investigator.