Pragmatic evidence and the nature of randomized trials

Pragmatic trials are increasingly gaining recognition. However, what pragmatic trials are is frequently misunderstood. They are frequently described superficially by their manifestation and surface only, as studies conducted in "real world" settings, having wide inclusion criteria, and less complicated study procedures. However, these features are neither necessary nor defining characteristics. They also do not guarantee that trials sharing them are useful to inform medical practice. There is a danger of losing sight of the essence of the powerful pragmatic approach.

Here we describe the key elements of the pragmatic approach and the close relationship with the original nature of randomized trials. Our aim is to refocus teaching, research and interpretation of evidence, not as a novel approach but as a return towards the essence of pragmatic evidence and the nature of randomized trials. We first go back to the origin of pragmatism in philosophy and its introduction in medicine and revisit the nature of randomized trials in their pure form. We highlight the critical distinction between assessing treatment decisions and understanding the mechanisms of these decisions. We show why the current view on randomized trials in medicine has lost a pragmatic focus, with the explanatory design features blinding and adherence control often seen as defining characteristics or quality criteria of randomized trials. We then highlight common misunderstandings of pragmatic trials and conclude with an overview of their key features to provide pragmatic evidence.