Limitations
This review has a few limitations regarding the material and methods and available evidence. First of all, there was a high heterogeneity between the included studies in terms of population, type of disease, which inequality was being addressed and outcome, making it difficult to group these studies and draw definite conclusions. Moreover, because various outcome measures were used it was not always possible to obtain objective or numerical results and therefore subjective interpretation may have taken place. Finally, bias might have occurred due to the publication of studies which showed an effect of socioeconomic, ethnic or environmental inequalities on PICU outcome.