Research note. Open letter to the users of the new PubMed: a critical appraisal

PubMed is a free database used daily by about 2.5 million people to search and retrieve scientific documents related to Health Sciences. In May 2020, certain changes were made to its search algorithm, which at first sight improves the location of scientific articles, but upon analyzing its operation in more depth, we detected some changes that make the reproducibility of bibliographic searches difficult. In order to safeguard the reproducibility and replicability of the searches carried out for systematic reviews, narratives and meta-analyzes, we suggest accompanying these strategies with a file in a format compatible with reference managers, to facilitate comparison and verification of the strategy to be replicated in a future.