[Introduction to the indirect meta-analyses].

Meta-analyses are studies that aim to compile all available information, grouping them according to an specific theme and evaluating it through methodological quality tools. When there are two specific comparisons of treatments based on randomized clinical trials, standard meta-analyses are the best option, but there are scenarios in which there is no available literature for those direct comparisons. In these cases, an alternative method to consider is indirect comparison or indirect meta-analyses. The aim of this review is to understand the conceptual foundations, the need, applications and limitations of indirect comparisons for further understanding of network meta-analyses.