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Bibliographic Services Division (BSD)

Index Section

The Index Section supports the biomedical research community by making it easier for users to find the journal articles they need in MEDLINE, the National Library of Medicine’s biomedical and life sciences database. To meet this goal, Index Section staff members and contract staff use a combination of human data review and indexing and machine processing to:

  • Add descriptive data to MEDLINE citations when not supplied by the publisher
  • Correct descriptive citation data when not corrected by the publisher
  • Add subject metadata to citations using the Medical Subject Headings, or MeSH
  • Create links between the NCBI Gene database and MEDLINE citations to describe new gene information
  • Create and index Supplementary Concept Records for drugs, proteins, and other chemicals not included in MeSH
  • Review the subject metadata to ensure that it is accurate.

Human indexing is a 150-year-old tradition at NLM. Since 2002, this expertise has been combined with Natural Language Processing technology to curate the biomedical literature more efficiently and consistently through the NLM Medical Text Indexer (MTI) system.

For more information about MEDLINE data review and indexing, see:

Indexing Statistics


The Indexing Process


Journals Information


Data Policies

Last Reviewed: June 22, 2018