Skip Navigation Bar
The World's Largest Medical Library
NLM Classification 2012: Worldwide source of medical library classification

About the NLM Classification

Scope of Revision
Historical Development
Structure of the NLM Classification
Relationship to MeSH®
Index

Scope of Revision

This edition incorporates all 2012 additions and changes to the schedules (see Class Numbers Added and Canceled) and to the index, which has been newly edited and updated with appropriate MeSH concepts. Eighty-eight (88) new index entries were created of which forty-six (46) are from the 2012 MeSH; the remainder are MeSH terms from previous years. Numerous main index entries and cross references were modified to reflect changes in the MeSH vocabulary. Two-hundred and eighteen (218) index entries were deleted.

Although the broad nature of the NLM Classification schedules precludes complete correspondence with MeSH, new class numbers were added and existing class numbers were canceled as needed to reflect other changes in MeSH and the biomedical and related sciences literature cataloged.

The QV (Pharmacology) schedule was the major area of focus for the 2012 edition.

Some QV schedule outline headers were changed, for example:

  • QV 610-618 Inorganic Poisons was changed to QV 610-666 Poisons
  • QV 627-633 Organic Poisons and QV 662-667 Gas Poisons. Chemical Agents were deleted

Some QV class number captions and notes were revised to better reflect the scope of the number. For example:

  • At QV 38, the caption Drug action was changed to Drug metabolism. Pharmacokinetics.
  • At QV 95, the caption Anti-inflammatory analgesics was changed to Non-steroidal anti-inflammatory agents.
  • Disinfectants was removed from the caption at QV 220 and added to the caption at QV 250
  • At QV 240, the caption Dyes and related compounds used in diagnosis or as reagents, indicators, etc. was change to Coloring agents.
  • At QV 241, the caption Tars. Balsams was changed to Complex mixtures.
  • At QV 310, the caption Gases and their compounds was changed to Noble gases.
  • At QV 663, the caption Chemical agents was augmented with Chemical warfare agents.
  • At QV 772, the caption Non-prescription drugs was changed to Drug catalogs.
  • At QV 778, the caption Pharmaceutical processes. Drug compounding was changed to Drug delivery systems (General or not elsewhere classified).
  • At QV 800, the caption Vehicles was changed to Pharmaceutic aids.
  • At QV 785, the caption Types of pharmaceutical preparations. Dosage forms was changed to Drug delivery systems.
  • At QV 786, the caption Solutions was changed to Drug dosage forms (General or not elsewhere classified).
  • At QV 4, the note was added: Classify here works discussing both pharmacological phenomena and pharmaceutical preparations. Classify works on pharmacological phenomena only in QV 37.
  • At QV 55, the note was added: Class here general works on pharmaceutical preparations and works on specific drugs not elsewhere classified.

Table G (geographic breakdown) is now permitted with QV 736 and QV 737.

Changes were made to other class schedules. For example:

  • The schedule outline WQ 200-212 Pregnancy was augmented with Reproduction.
  • At WB 495, the caption Electric stimulation therapy was augmented with Magnetic field therapy.
  • At WE 190, Orthopedic procedures was removed from the caption and Traction was added.
  • At WN 415, Radioisotopes was removed from the caption.
  • At WO 62, and anesthesiologist was added to the caption.
  • Instructional notes were added or modified to clarify classification practices as needed. For example:
    • A note was added to QT 37: Cf. QU 300-328 Cell engineering.
    • A note was added to WE 168: Classify works on orthopedics as a profession in WE 21.
  • Table G (geographic breakdown) is now permitted with WA 320.

Changes were made to Table G (Geographic Notations).

  • Two (2) Table G numbers were added:
    • South Korea (JK6)
    • North Korea (JK7)
  • Korea was moved to the Historical Geographic Locations retaining the same Table G (JK6)

Historical Development

The genesis of the NLM Classification is a Survey Report on the Army Medical Library, published in 1944, which recommended that the "Library be reclassified according to a modern scheme," and that the new scheme be a mixed notation (letters and numbers) resembling that of the Library of Congress. Subsequently a classification committee was formed, chaired by Keyes D. Metcalf and including Mary Louise Marshall who compiled the schedules. Medical specialists acted as consultants to the committee. Based on the consultants' advice, that of the committee and of the NLM cataloging staff, Ms. Marshall produced a preliminary edition of the Library's Classification, which was issued in 1948.

The preliminary edition was revised by Frank B. Rogers and the first edition of the new classification was published in 1951 as the U.S. Army Medical Library Classification. It firmly established the current structure of the classification and NLM's classification practices. The headings for the individual schedules were given in brief form (e.g., WE - Musculoskeletal System; WG - Cardiovascular System) and together they provided an outline of the subjects that constitute the National Library of Medicine Classification . These headings were interpreted broadly as including the physiological system, the specialty or specialties connected with them, the regions of the body chiefly concerned and subordinate related fields. Within each schedule, division by organ usually has priority. All schedules, including some of their sections, are preceded by a group of form numbers representing publication types. These numbers, ranging generally from 1-39, are employed as mnemonic devices throughout the Classification.

Beginning with the 2002 edition, the National Library of Medicine Classification is published in electronic form and updated annually:

The online environment offers many advantages to users including hyperlinks between class numbers in the index and the schedules, and between terms within the index and direct links from these to the MeSH record itself under the MeSH Browser.

The online data creation and maintenance system of the Classification gives NLM the ability to update the classification annually in tandem with MeSH. Publication of printed editions ceased with the 5th revised edition, 1999. Beginning with the 2006 edition, the NLM Classification is also available in PDF (Portable Document Format) at http://www.nlm.nih.gov/class/terms_cond.html.

Structure of the NLM Classification

The National Library of Medicine Classification covers the field of medicine and related sciences, utilizing schedules QS-QZ and W-WZ, permanently excluded from the Library of Congress (LC) Classification schedules. The various schedules of the LC Classification supplement the NLM Classification for subjects bordering on medicine and for general reference materials. The LC schedules for Human Anatomy (QM), Microbiology (QR) and Medicine (R) are not used at all by the National Library of Medicine since they overlap the NLM Classification.

Relationship to MeSH

The schedules, with their special requirements for use with all types and forms of materials, preclude strict adherence to the hierarchical arrangement of the Medical Subject Headings (MeSH), the Library's thesaurus for indexing and cataloging. The schedules maintain their own character in order to provide for material, old as well as new, acquired for the Collection, including dictionaries, atlases, directories and other items, which are not suitable for the arrangements, found in MeSH. However, an effort was made to make schedule headings, subheadings and class number captions compatible with MeSH terminology. The MeSH Tree Structures were used extensively to determine the proper placement of a concept in a schedule and to relate index headings to one another. Since the representation of subjects in the schedules of the NLM Classification is intentionally broad, the captions do not enumerate all of the subordinate concepts that are to be classified in a given number. MeSH descriptors for these subordinate concepts do appear in the index, to the extent practical with appropriate references to the classification numbers.

Index

The Index to the NLM Classification consists primarily of Medical Subject Heading (MeSH) concepts used in cataloging. It includes concepts first appearing in the latest edition of MeSH and other older concepts as warranted by the literature cataloged. It also provides access to classification numbers through these MeSH concepts. Index entries are updated annually to reflect additions and changes of the latest edition of MeSH. For additional information on the Index see About the Index.