he Medical Subject Headings (MeSH) Translation Table used in PubMed's Automatic Term Mapping has been enhanced to include Publication Types (PT) and their Entry Terms. For more information about Automatic Term Mapping, please see PubMed's Help. This change will improve citation retrieval by publication type. Unqualified terms in a query will be searched as follows:

• For a term represented by both a MeSH Heading (MH) and a Publication Type (PT), when the user enters the MH, the PT, or any of their Entry Terms, PubMed will map as follows:
  
  Publication Type [PT] OR MeSH Term [MH] OR Term Entered by User [TW]
  
  For example, when a user enters: clinical trials
  PubMed will search:
  ("clinical trial"[Publication Type] OR "clinical trials"[MeSH Terms]) OR "clinical trials"[Text Word]
  
  
• For a term represented only by a PT, when the user enters the PT or one of its entry terms, PubMed will map as follows:
  
  Publication Type [PT] OR Term Entered by User [TW]
  
  For example, when a user enters: commentary
  PubMed will search:
  ("comment"[Publication Type] OR "commentary"[Text Word])

Background information:
Publication Type (PT) values are added to the MEDLINE citation during indexing to indicate the article's type of information or the manner in which it is conveyed. There are fifty-three publication types used for indexing (a complete list is available in PubMed Help). Twenty-seven of those PTs have a MeSH counterpart that is either the same (e.g., biography[pt], biography[mh]) or very similar (e.g., clinical trial[pt], clinical trials[mh]).

In the past, for most concepts represented by both MH and PT, when users entered an unqualified term, PubMed searched for the MH and the term entered as Text Word (TW). For example, if the user entered biography, PubMed searched for: ("biography"[MeSH Terms] OR biography[Text Word]), thus missing most citations indexed to Biography[Publication Type]. When users entered an unqualified term that was only represented by a PT, it was searched as "All Fields." As PT is included in All Fields, users retrieved citations indexed with the PT plus some false drops. A search using a PT Entry Term did not retrieve the publication type because PT Entry Terms were not recognized in PubMed. For example, Comment was not retrieved if commentary was entered.

Note: Overall is a publication type and a stopword in PubMed. Users wishing to retrieve the publication type Overall, will need to qualify their query (e.g., overall[pt]).

By Norma I. Ruiz
MEDLARS Management Section

Ruiz NI. PubMed^®: Publication Type Mapping. NLM Tech Bull. 2003 Mar-Apr;(331):e1.