Non-interventional clinical studies are a special type of scientific medical studies that bear little resemblance to traditional interventional randomized clinical trials. Since the middle of the 20th century, RCTs have been quite strictly regulated by the State Authorities in the countries in which they are actively carried out. Non-interventional clinical studies, on the contrary, have for a long time remained without any special regulations and out of the attention of the regulatory authorities. On a practical level, there is often confusion being observed in determining the category to which a study belongs, i.e. whether a project should be referred to the type of interventional or to the type of non-interventional studies (NIS). The article analyzes the changes, made to approaches to understanding NIS, formulates the key criteria for identifying the types of studies. The impact of the changes in the concept of non-interventional clinical studies on the development of this area is shown in the article.

clinical study, non-interventional study, NIS concept, regulation, identification criteria.