This article summarizes notable data changes made to MEDLINE during the National Library of Medicine’s annual Year-End Processing (YEP) maintenance for 2020:
The MeSH Browser currently points to the 2020 MeSH vocabulary with a link to the 2019 MeSH vocabulary. Searchers should consult the Browser to find MeSH headings of interest and their relationships to other headings. The Browser contains MeSH heading records that may include Scope Notes, Annotations, Entry Terms, History Notes, Allowable Qualifiers (Subheadings), Previous Indexing, and other information. It also includes Subheading records and Supplementary Concept Records (SCRs) for substances, diseases, and organisms that are not MeSH headings. You can download 2020 MeSH from links on the NLM Data Distribution page for MeSH Data. The PubMed MeSH database and translation tables will be updated to reflect 2020 MeSH by the middle of December when YEP activities are complete and the newly maintained MEDLINE data are available in PubMed.
For 2020, 97 MeSH headings were either changed or deleted and replaced with more up-to-date terminology. During YEP, NLM updates these MeSH headings on MEDLINE citations. 293 new MeSH headings, plus two new Publication Types, are added to MeSH in 2020. A complete list of the new 2020 MeSH headings is available in PDF format, visit New Headings with Scope Notes, Annotations and Tree Locations.
Typically, NLM does not retrospectively re-index MEDLINE citations with new MeSH heading concepts. Therefore, searching PubMed for a new MeSH term tagged with [mh] or [majr] effectively limits retrieval to citations indexed after the term was introduced. PubMed Automatic Term Mapping (ATM) expands an untagged subject search to include both MeSH Terms and All Fields index terms and may retrieve relevant citations indexed before the introduction of a new MeSH term. Searchers may consult the MeSH Browser or the MeSH database to see the previous indexing terms most likely used for a particular concept before the new MeSH Heading was introduced.
One new publication type is available for MEDLINE indexing in 2020:
For a complete list of updates, visit the NLM Technical Bulletin.