Propensity score matching (PSM) is an increasingly applied method of ensuring comparability between groups of interest. However, PSM is often applied unconditionally, without precise considerations. The purpose of this study is to provide a nonmathematical guide for clinicians at the stage of designing a PSM-based study. We provide a seed of thought for considering whether applying PSM would be appropriate and, if so, the scope of the list of variables. Although PSM may be simple, its results could vary substantially according to how the propensity score is constructed. Misleading results can be avoided through a critical review of the process of PSM.
Keywords: Indication bias; Observational study; Propensity score; Propensity score matching; Selection bias.