Evidence level of clinical interventional studies-Mind the biases

All clinical trials can be subject to biases, which need to be considered when interpreting the results. Biases can arise in all clinical studies and influence the results of the investigation in a relevant way. These biases can occur in the selection of the study cohort, by the investigators, the collection and the analysis of the data. The aim of this article is to describe frequently occurring biases in clinical interventional studies and to provide guidance on how to identify them in order to facilitate the evaluation of the literature.