Medical Subject Headings
MeSH Record Types
The following is a list of the three basic types of MeSH Records: Descriptors, Qualifiers, and Supplementary Concept Records (SCRs). Publication Characteristics, while technically a Descriptor, are also included since they function differently in some ways than a subject heading.
Also known as Main Headings, Descriptors are used to index citations in NLM's MEDLINE database, for cataloging of publications, and other databases, and are searchable in PubMed as [MH]. Most Descriptors indicate the subject of an indexed item, such as a journal article, that is, what the article is about. Descriptors are generally updated on an annual basis but may, on occasion, be updated more frequently.
- Publication Characteristics (Publication Types)
Although MeSH Descriptors, these records are unlike other MeSH Descriptors in that they indicate what the indexed item is, i.e., its genre, rather than what it is about, for example, Historical Article. May include Publication Components, such as Charts; Publication Formats, such as Editorial; and Study Characteristics, such as Clinical Trial. These data are data about the data, rather than being about the content. Unlike other Descriptors, these records are searchable in PubMed as Publication Type [PT], and the terms in MEDLINE records are labeled as "PT" or <PublicationType> rather than "MH" or <MeSHHeading>. MeSH Descriptor Class = 2. They are listed in category V of the MeSH Tree Structures. A list is available of Publication Types, with Scope Notes.
Descriptors which include continents, regions, countries, states, and other geographic subdivisions. They are not used to characterize subject content but rather physical location. MeSH Descriptor Class = 4. They are listed in category Z of the MeSH Tree Structures.
There are 83 topical Qualifiers (also known as Subheadings) used for indexing and cataloging in conjunction with Descriptors. Qualifiers afford a convenient means of grouping together those citations which are concerned with a particular aspect of a subject. For example, Liver/drug effects indicates that the article or book is not about the liver in general, but about the effect of drugs on the liver Qualifiers are searchable in PubMed as MeSH Subheadings [SH].
- Qualifiers, with Scope Notes
- Qualifiers by Allowable Category (also known as AQ Lists)
- Qualifier Hierarchies
Qualifiers are generally updated on an annual basis.
- Supplementary Concept Records
Supplementary Concept Records (SCRs), formerly called Supplementary Chemical Records, are used to index chemicals, drugs, and other concepts for MEDLINE and are searchable by Substance Name [NM] in PubMed. Unlike Descriptors, SCRs do not have Tree Numbers, however, each SCR is linked to one or more Descriptors, usually broader, by the Heading Mapped To field in the SCR. SCRs are updated weekly, unlike Descriptor and Qualifier records, which are generally updated on an annual basis. There are currently over 170,000 SCR records with over 440,000 SCR terms. Like all MeSH records, SCRs are searchable in the MeSH Browser.