How to Stay Updated on Yearly Changes to MEDLINE

It’s that time of the year again.  No, not fall, Halloween, or the beginning of the Christmas shopping season (that started in July); it’s time for the annual MEDLINE®/PubMed® Year-End Processing (YEP) activities.  If you look at the Major Recent Updates section of the MEDLINE system report on Intellogist, you’ll notice that during September of 2011 and 2012, there are mentions of an annual update to the Medical Subject Headings (MeSH), the controlled vocabulary for MEDLINE. The yearly MeSH update is one part of the YEP activities that occur every fall.  The MEDLINE file is a central resource for biomedical prior art that can be freely accessed through the PubMed interface, so patent searchers should be aware of the updates made annually to the database and its controlled vocabulary, as well as how these changes may affect their prior art searches.

After the jump, learn all about the year-end processing activities for MEDLINE and how these changes may affect your searches on PubMed!

What are MEDLINE Year-End Processing (YEP) activities?
MEDLINE is regularly updated each day Tuesday-Saturday with citations indexed with MeSH.  During the fall of each year, the National Library of Medicine (NLM) performs additional maintenance to MEDLINE data, known as year-end processing (YEP).  According to the NLM website:

This maintenance is primarily to make changes to the Medical Subject Headings (MeSH®) on existing MEDLINE citations to conform to the forthcoming year’s version of MeSH, and also involves other global changes such as those to Supplementary Concept Substance Names.

The YEP procedures usually occur from mid-November to mid-December, and during this period “the schedule for adding citations newly indexed with MeSH and revised citations to MEDLINE/PubMed is temporarily interrupted, and no newly indexed or maintained versions of MEDLINE citations are added to PubMed” (although in-process citations continue to be added).  After the YEP activities are completed, the new version of MEDLINE (with the new year’s MeSH headings) is loaded to PubMed, and the regular MEDLINE update schedule resumes.

The NLM website lists a number of recurring annual changes to MeSH  and MEDLINE that may occur during YEP:

  • Brand New Concepts
  • Replaced-by heading; old heading retained as entry term to new heading
  • Replaced-by heading; old heading deleted and not retained as entry term to new heading; adjustments to search strategies needed
  • Deleted Heading with Follow-On Adjustments
  • Deleted Heading; old heading is retained as an entry term for the new headline
  • Deleted heading; old heading becomes entry term to new heading but new heading not equivalent in meaning to old headings
  • Entry Terms (See References) changes
  • Other MeSH changes that are made during year-end processing
    • Publication Types
    • Identification of Clinical Trials in MEDLINE
    • Entry Combination Revisions
    • Heading Mapped-To (HM) Maintenance
    • EC/RN Numbers (RN) and Name of Substance (NM)
    • Supplementary Concept Records (SCRs) Elevated to MeSH Headings
    • Pharmacological Action (PA) Added to Supplementary Concept Records

Where can I learn about these updates?

The two main resources for learning about YEP updates to MEDLINE, MeSH, and PubMed, are the Annual MEDLINE®/PubMed® Year-End Processing (YEP) section of the NLM website and the the NLM Technical Bulletin.  The YEP section of the NLM website describes how the YEP procedures will affect indexed citations, in-process citations, searching, and corrections on hold in MEDLINE.  This page also lists important dates, NLM Technical Bulletin articles, and additional articles related to YEP procedures.  Finally, the page links to the general information section “What is YEP?“, which gives a general description of the YEP procedures and schedule (paraphrased above), as well as explanations and examples of recurring annual changes to MeSH.

The NLM website provides background information on YEP procedures for MEDLINE.

The “What is YEP?” section lists articles that will appear in the NLM Technical Bulletin on an annual basis which relate to YEP procedures:

  • MEDLINE®/PubMed® Year-End Processing (YEP) Activities – September-October
  • MEDLINE® Data Changes – November-December
  • What’s New for MeSH – November-December
  • PubMed® Notes – November-December
  • Articles in the November-December issue that address changes to LocatorPlus and NLM Catalog, which may be different from MEDLINE.

The NLM Technical Bulletin articles will keep users up-to-date on specific annual MEDLINE changes and give users access to the most recent versions of MeSH.  For example, in September 2012, the NLM Technical Bulletin published an article titled 2013 Medical Subject Headings (MeSH) Now Available, which links to the introduction to MeSH 2013 and the option to download 2013 MeSH in XML and ASCII formats.

Check the NLM Technical Bulletin for updates on YEP progress and links to new versions of MeSH.

How Will YEP changes affect my searches?

The YEP page on the NLM website gives the following explanation of how the year-end processing procedures will affect MEDLINE searches between mid-November and mid-December:

A search limiting terms to fields affected by indexing (e.g., telemedicine [mh]) does not retrieve in process or publisher-supplied records (see Data added to MEDLINE records during indexing). Therefore, during end-of-year activities when we are not adding completed, indexed citations to MEDLINE/PubMed, such searches – including those stored in My NCBI and retrieved through RSS feed stored searches – may not retrieve new records for some weeks. To retrieve new, in process records during this time, you should use searches that do not limit to affected fields (e.g., telemedicine). Note that the search terms are not tagged in this example.

Users need to be cautious when constructing their MEDLINE search query during this period between mid-November and mid-December each year, so as not to miss in-process citations.


MEDLINE is a well-maintained file that is updated on a very regular schedule, with a major update of the controlled subject headings completed on an annual basis.  This major annual update for MEDLINE and the medical subject headings (MeSH), called year-end processing, disrupts the regular update schedule for indexed citations.  Fortunately, the NLM website provides a resource to guide searchers in creating queries that will pick up recent in-process citations, and the NLM Technical Bulletin keeps searchers updated on the progress of the YEP activities.  Professional patent searchers will always locate the most recent and relevant prior art by following changes to important databases and search platforms like MEDLINE and PubMed, so continue to check Intellogist for recent updates on the most important sources of patent and non-patent literature!

Do you know of other resources provided by the National Library of Medicine that will help prior art searchers stay updated on recent changes to MEDLINE and PubMed?  Let us know in the comments!

Patent Analysis from Landon IP

This post was contributed by Joelle Mornini. The Intellogist blog is provided for free by Intellogist’s parent company Landon IP, a major provider of patent searches, trademark searches, technical translations, and information retrieval services.

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