[Propensity score: Interests, use and limitations. A practical guide for clinicians]

Propensity scores have been proposed in the early 1980s, and are increasingly used in epidemiology since the 2000s. They are is used to minimize the selection bias in observational studies, leading to a comparability between the exposure groups close to that observed in randomized trials. However, they have important limitations. Besides, new statistical techniques to improve the propensity score performances are more and more complex, while the build and the use of propensity score require a strict methodology to avoid bias, imprecision and non-reproducibility. This overview, designed for clinicians, is aimed at describing the advantages, techniques of use and limitations of propensity scores. A reading grid is provided in order to help interpreting studies using propensity scores.