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September 29, 2005 [posted]
June 04, 2006 [Editor's note added]

MEDLINE®/PubMed® End-of-Year Activities

[Editor's Note: End-of-Year activities completed on December 12, 2005. See Newly Maintained MEDLINE® Now Available in PubMed®

the National Library of Medicine® (NLM® ) is currently involved in MEDLINE year-end processing activities. These include changing the Medical Subject Headings (MeSH® ) on existing MEDLINE citations to conform with the 2006 version of MeSH, and other global changes such as those to Supplementary Concept Substance Names. Check the forthcoming issues of the NLM Technical Bulletin for an article about 2006 MeSH changes.

According to the normal MEDLINE/PubMed update schedule, MEDLINE citations are released and revised Monday through Friday, and these citations are then available to MEDLINE licensees and PubMed users Tuesday through Saturday. During end-of-year activities, NLM's schedule for adding indexed citations to MEDLINE and PubMed is temporarily interrupted. Once the end-of-year activities are complete (tentatively targeted for December 2005), the normal MEDLINE/PubMed update schedule will resume, and PubMed will use 2006 vocabulary in the MeSH translation tables and MeSH database, as well as in the citation data.

Indexed Citations

On November 17, 2005, NLM expects to halt temporarily the addition of fully-indexed MEDLINE citations to PubMed. NLM indexing staff will continue to index citations, but these records will be held and not added to PubMed until the normal update schedule resumes.

In-Process Citations

During end-of-year activities, "in-process" citations will continue to be added to PubMed. As a result, the number of PubMed records labeled [PubMed - in process] will temporarily increase. These citations do not have MeSH terms, but they have undergone issue level and subsequent citation level quality control reviews.


A search limiting terms to fields affected by indexing (e.g., fibromyalgia [mh] AND review [pt]) does not retrieve in-process or publisher-supplied records (see list of fields added, changed, or supplemented 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., fibromyalgia review). Note that the search terms are not tagged in this example.

By December, the in-process citations that are within the scope of MEDLINE and that have been indexed since November 17, 2005 will be replaced as indexed citations with 2006 MeSH terms, Publication Types, etc. Searches, including My NCBI Stored Searches, containing tagged search terms will then retrieve all applicable MEDLINE records.

Corrections on Hold

Also as of November 17, 2005, corrections to completed MEDLINE citations (e.g., to correct an author name misspelling) will not be released to MEDLINE. NLM staff will continue to correct completed citations and these will replace the incorrect citations in MEDLINE when the normal update schedule resumes.

Data (with search tags) added to MEDLINE records during indexing:

EC/RN Number [rn]

Grant Number [gr]
Note: Some grant numbers are added during indexing, but the majority are added while the citation is “in process.”

MeSH terms [mh] (includes age groups; Humans/Animals; Male/Female)

MeSH Major Topic [majr]

Publication Type [pt]
Note: Some publication types are present on in process records but many are added during indexing.

Subheadings [sh]

Subset [sb] (citation status values change from “In Process” to “MEDLINE” once MeSH indexing has been completed)

Substance Name [nm]

Note: English [la] is not on this list. Limiting to English language will retrieve in-process records.

Other changes of note coming for MEDLINE/PubMed

The majority of MEDLINE data changes will be covered in a forthcoming NLM Technical Bulletin article, to be titled "MEDLINE Data Changes - 2006." However, here is some information worth knowing in advance.

For the 2006 indexing year, NLM will be implementing the following indexing policy changes:

1) Redundant indexing will no longer be done for the specifics now treed under the following publication types:
a) Clinical Trial
b) Guideline
c) Consensus Development Conference

NLM has decided that these "parent" publication types no longer need to be assigned for prospective citations when one of their narrower publication type terms is assigned to a record because, with 2006 MeSH, publication types are assigned tree numbers for the first time. Tree numbers, which act as placeholders in the hierarchy enable the "explode" capability for retrieval in search systems. For example: Clinical Trial will no longer be added when one of the more specific clinical trial terms such as Controlled Clinical Trial or Randomized Controlled Trial is used; and Guideline will no longer be added when Practice Guideline is used. The new MeSH category, called the V Category, contains all the publication types and a few MeSH headings (known as check tags) that did not have tree numbers before. Only Male and Female remain as MeSH headings without tree numbers in 2006 MeSH.

2) Redundant indexing will no longer be done for the specifics now treed under the following MeSH Headings:
a) Aged
b) Research Support, U.S. Gov't, P.H.S.

The parent term Aged will no longer be automatically added to the MeSH Heading field for prospective records indexed with the term Aged, 80 and Over. Also, the MeSH Heading Research Support, U.S., Gov't, P.H.S. will no longer be added when the more specific tag Research Support, N.I.H., Extramural is used. These research support terms have been given tree numbers with 2006 MeSH, and, consequently, the ability to explode the term will allow users to get comprehensive retrieval without requiring redundant indexing.

By Sara Tybaert
MEDLARS Management Section

Tybaert S. MEDLINE®/PubMed® End-of-Year Activities. NLM Tech Bull. 2005 Sep-Oct;(346):e4.

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