NLM performs daily routine maintenance of MEDLINE data. In the fall of each year NLM performs additional maintenance to MEDLINE data, known as Annual MeSH Processing, or AMP. AMP encompasses extensive changes to MEDLINE citations. The primary function of AMP is to update the Medical Subject Headings (MeSH) on existing MEDLINE citations to conform with the upcoming version of MeSH, which is released annually in early December. Changes are made to MeSH descriptors (main headings), qualifiers (subheadings), and Supplementary Concept Records (SCRs), which are standardized names and associated numbers for chemicals, protocols, diseases, organisms, population groups, and anatomical structures that map to MeSH descriptors. Other global changes to MeSH headings may be made during AMP as well.
The nine MeSH update reports listed below detail the changes to MeSH terms that are performed during AMP. These processing procedures usually start in early December when the annual MeSH update files are released and are targeted for completion by the middle of December. When AMP activities are complete, the new version of MEDLINE, with the new year's MeSH Headings, is loaded into PubMed, and the regular MEDLINE/PubMed update schedule resumes. At this point PubMed uses the new year's MeSH vocabulary in the MeSH translation tables and the MeSH database.
The resources listed below provide additional information on MeSH and MeSH Annual Processing.
Annual MeSH Processing (AMP) Resources