Why do we need observational studies of everyday patients in the real-life setting?

Randomized controlled trials (RCTs) are performed with the primary goal of understanding the safety and efficacy of a new therapy in a selected group of patients. Even when evidence from these studies strongly favours a new therapy, its role in routine clinical practice may be unclear because of the considerable differences between its efficacy (in clinical trials) and its effectiveness (in the real-life setting). Real-life studies are observational studies that are essential to document benefits and harms of therapy in a wider population and to determine whether patients in routine practice are achieving expected outcomes. In the first article of this supplement, we discuss the relative strengths and limitations of RCTs and real-life studies and explore the current and potential uses of real-life studies in the field of thrombosis, including identifying new safety signals, assessing outcomes in special populations and raising questions about factors affecting medication adherence and persistence. Real-life studies provide a bridge from the results of RCTs to daily clinical practice.