​Non-interventional prospective studies (NIS) are prospective studies which are set up to investigate events that will take place after the study has been initiated. The main and very important difference between a clinical trial and a NIS is that the data collection or patient-participation in the NIS does not interfere with the choice of treatment, sample collection, procedures, and the treatment itself, which entirely follow standard hospital practices.  

The main advantage of a prospective study is that the selection of patients is done a priori, following certain eligibility criteria, with the potential to follow them until the end of the study. With a NIS the bias due to patient selection by unknown circumstances may not be completely prevented, but will be small compared to retrospective studies. Apart from that, in a NIS, collection of MED C data is easier than in retrospective studies as the centres do not have to get back to their files. 

As the patients in this type of study will receive the same treatment and diagnostic procedures as they would have received if they were not included in this study, ethical approval might not be needed. A NIS is always strictly observational. However, regulations differ per country. Please contact your Ethics Committee in case of any doubts.