Credibility of clinical research depends on consensus on outcomes

In clinical studies, beneficial and harmful effects of interventions are investigated by measuring predefined outcomes. The uncontrolled choice of these outcomes carries a risk of outcome reporting bias, large heterogeneity of outcomes with reduced options for evidence synthesis. Furthermore, such outcomes may not be important for stakeholders including patients. A potential solution to these problems is to develop a core outcome set (COS) - a list of outcomes which have been estimated to be important to include in all future studies in a given setting by all relevant stakeholders. This review summarises the benefits of defining a COS.