Principles of MEDLINE Subject Indexing
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To better understand how to use MeSH when searching MEDLINE, it is helpful to understand the basic principles of subject indexing for MEDLINE.
Subject indexing includes:
- reviewing a journal article (or other material such as a letter or editorial)
- determining its subject content, and
- describing that content using a controlled vocabulary.
Purpose of indexing with controlled vocabulary:
- to facilitate search retrieval by eliminating (or accounting for) the use of variant terminology for the same concept.
Types of vocabulary terms:
- 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), gender, 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 (Animals, Humans, Male, Female, In Vitro, Comparative Study, and research support terms) can never be designated as the main point of the article
- A special class of MeSH headings
that must be considered routinely for every 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/searching of chemicals (in the broadest sense) which are not MeSH headings
Philosophy of indexing
- The content and format of each item are fully and adequately described
- The most specific vocabulary terms are used
- The indexer’s job is only to index, not to interpret, evaluate or diagnose
