Structured Abstracts in MEDLINE

Structured abstracts contain distinct labeled sections (e.g., “RESULTS”) for key information from articles they summarize.  If English-language structured abstracts appear in journals that the US National Library of Medicine (NLM) indexes, the labels in these abstracts usually appear in all uppercase letters, generally followed by a colon, in MEDLINE/PubMed citations.  Nearly a quarter of all abstracts added to the MEDLINE/PubMed database include section labels.  These structured abstracts are reformatted for easier readability in PubMed such that uppercased section labels are bolded and each section begins on a new line.

Legitimate structured abstract labels that have been identified are mapped to one of five broad conceptual groups (Metacategories): BACKGROUND, OBJECTIVE, METHODS, RESULTS, and CONCLUSIONS.    The  2011 NLMMedlineCitationSet DTD and MEDLINE/PubMed XML accommodate structured abstracts as a part of NLM data dissemination so that licensees can manipulate the display and searching of structured abstracts. This Structured Abstracts in MEDLINE® resource provides access to datasets of Structured abstract Label Lists and NLM Category Mappings files and Implementation documentation for interested Developers or Researchers.


Anna Ripple
Jim Mork
Lou Knecht

Associated Institutions

U. S. National Library of Medicine

Application Domains
  • Literature
Other Resource Type
Software Subtype
Programming Languages
Operating Systems
Included Components
Dataset Subtype
  • Human annotated
  • Machine annotated
  • Structured data
Data Model Subtype
Online Resource Subtype
Knowledge Base Subtype
Intended User Types
  • Informatics researcher
  • NLP researcher or developer
  • Software developer

Ripple AM, Mork JG, Knecht LS, Humphreys BL. A retrospective cohort study of structured abstracts in MEDLINE, 1992-2006. J Med Libr Assoc. 2011 Apr;99(2):160-3. PubMed PMID: 21464855; PubMed Central PMCID: PMC3066587.
Ripple AM, Mork JG, Knecht LS. Structured Abstracts: A New Look for the PubMed® Abstract Display. NLM Tech Bull. 2010 Jul-Aug;(375):e11.
Harbourt AM, Knecht LS, Humphreys BL. Structured abstracts in MEDLINE, 1989-1991. Bull Med Libr Assoc. 1995 Apr;83(2):190-5. PubMed PMID: 7599584; PubMed Central PMCID: PMC226026.

Available Documentation
Development Milestones

Updated Label List and NLM Category Mappings File (August 26, 2011)