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Principles of MEDLINE Subject Indexing

The types of vocabulary terms are:

  • MeSH headings ("descriptors")
  • Subheadings ("qualifiers")
  • Check tags 
    • A special class of MeSH headings that must be considered routinely for every article
      • Primarily headings covering species (including Humans), sex, and human age groups
      • Also cover:
        • historical time periods
        • pregnancy
    • Usually are indexed even if merely mentioned, unlike other MeSH headings
    • For review articles, usually are indexed only if the main point of the article
    • Humans is not selected for articles involving institutions that serve humans, e.g., clinics, hospitals
    • Some check tags (e.g., Animals, Humans, Male, Female) can never be designated as the main point of the article
  • Publication Characteristics (or Types): describe the item being indexed rather than its topic.   There are 3 main categories:
    • Publication Components, e.g., English Abstract
    • Publication Formats, e.g., Lectures, Letter
    • Study Characteristics, e.g., Clinical Trial, Twin Study
  • Supplementary Concept Records: allow the indexing and searching of non-MeSH headings, primarily substances but also some protocols, some virus terms and rare disease terms. 
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