his is the time of the year when NLM's schedule for adding indexed citations to MEDLINE changes to accommodate NLM's internal maintenance cycle known as Year-End Processing (YEP). This year NLM is also engaged in the major task of replacing our system that manages the data entry, indexing, and quality control of journal citations. While both these tasks are in progress we have stopped adding fully indexed citations to our MEDLINE database.

In Process Citations
Although NLM staff continue to index citations, no citations in PubMed have been elevated to MEDLINE status since November 7, 2000. As a result, the number of PubMed records labeled [MEDLINE record in process] will increase during this period as we continue to add in process citations to PubMed. These "in process" citations do not have index terms (e.g., MeSH terms), and the bibliographic citation data (e.g., pagination values) have not been checked for quality control.

In early 2001, PubMed will be updated and the in process citations that are within the scope of MEDLINE will be replaced by indexed citations with MeSH terms, Publication Types, etc. Also, the citation bibliographic data will have been checked for accuracy.

This growing pool of unindexed citations is important to note for searchers who have chosen certain search terms from PubMed's Limits feature, e.g., Human, or who have qualified search terms for fields that are added to the citation during NLM's indexing process.

Example: robotics [mh] AND review [pt]

(See a list of other fields added or supplemented during indexing at the end of this article.)

Please note that a search limiting terms to fields affected by indexing will never retrieve in process or publisher supplied records. However, during this period when we are not adding citations to MEDLINE, searchers, including those using the Cubby to store searches, may not understand why they may not be retrieving new records for many weeks. Searchers may want to consider not limiting their searches using impacted fields, e.g., [mh] or [pt] for this period.

If you are not tagging search terms (example: robotics review) or using limits in your search, this will not be a concern for you. Searches containing qualified search terms will retrieve all applicable MEDLINE records when run after PubMed has been updated in early 2001.

Corrections on Hold
Corrections to MEDLINE are also "on hold" for this period. If you or one of your patrons recently reported an error on a MEDLINE citation to us, e.g., a misspelling of an author's name, this will not be corrected until PubMed is updated in early 2001.

2001 Version of MEDLINE
We will soon publish an NLM Technical Bulletin article detailing changes for MEDLINE as well as the 2001 update schedule. MEDLINE will undergo the traditional upgrade of changing the MeSH Headings to agree with the 2001 version of MeSH, along with other global changes such as necessary journal title abbreviation edits or Supplementary Concept Substance Name edits. In addition this year, other changes are expected as a result of the new data creation and maintenance system. Expected dates for these changes to appear in PubMed as well as for the 2001 PubMed MeSH Browser and translation tables will be announced soon.

By Annette M. Nahin
MEDLARS Management Section
and
Lou Knecht
Bibliographic Services Division

Nahin AM, Knecht L. MEDLINE Indexed Citations and Corrections Temporarily on Hold. NLM Tech Bull. 2000 Nov-Dec;(317):e3.