Classification 2021 Winter Edition

Worldwide source of medical classification resources

Scope of Revision of the 2021 Winter Edition

The major focus of the 2021 winter edition was the evaluation of the 2021 MeSH (Medical Subject Headings) vocabulary for inclusion in the Classification index. Several additions and changes were made to the Index and Schedules based on this review. All main index headings are now linked to the 2021 vocabulary in the MeSH Browser. Additional minor updates were made to the Index and Schedules.

Summary Statistics for the 2021 Winter Edition

  • 51 index main headings added (46 from 2021 MeSH)
  • 48 index entries modified
  • 1 index heading deleted
  • 28 class numbers added
  • 23 class number captions or notes modified
  • 1 class number canceled

Examples of Additions and Changes Based on MeSH 2021

Summary of COVID-19 related changes 

4 new index terms

5 modified index terms

11 new class numbers

2 modified class numbers

1 cancelled class number

  • The virus, SARS-CoV-2, was added to an existing number, QW 168.5.C8 Coronaviridae
  • The disease, COVID-19, was added to the index at a new number in the viral respiratory tract infections area: WC 506.  A breakdown of 8 new subordinate WC 506 class numbers were created to cover the various aspects of COVID-19 like the breakdown under AIDS at WC 503.
  • A new nursing number was created for COVID-19 nursing: WY 153.7
  • COVID-19 Testing was added to the index and classed at one of the new COVID-19 numbers: WC 506.1 Diagnosis. For consistency sake, some changes were made to the classification of serodiagnosis of other diseases:
    • QY 275 Syphilis serodiagnosis was cancelled.
    • Syphilis Serodiagnosis is now classed with Syphilis in the new number: WC 160.5 Diagnosis
    • AIDS Serodiagnosis was moved from QY 265 Serologic tests (General) and is now classed with AIDS diagnosis at WC 503.1
  • COVID-19 Vaccines was added to the index and classed at one of the new COVID-19 numbers: WC 506.6

Other E1 Diagnosis Terms Added

  • HIV Testing WC 503.1 (classed with HIV/AIDS diagnosis; now AIDS Serodiagnosis is classed here as well)
  • Clinical Reasoning WB 142.5
    • Treed under Clinical Decision-Making (currently classed at WB 141)
    • Since WB 141 is a heavily populated number, a new number was created for the parent term, Clinical Decision-Making at WB 142.5

Summary of Neurobehavioral Manifestations Changes

  • In 2020 MeSH, Mania was an Entry Term to Bipolar Disorder (classed at WM 171.7). With MeSH 2021, Mania is a new term treed under Neurobehavioral Manifestations (classed at WL 340).
  • A review of all the terms classed under Neurobehavioral Manifestations was conducted to see if there was enough literary warrant to create a new class number for this parent term.
  • As a result of this analysis, a new class number WL 340.1 was created for Neurobehavioral Manifestations. This new number is indented under WL 340 Neurologic manifestations (General or not elsewhere classified).
  • Mania and several existing terms in the class index that tree under Neurobehavioral Manifestations are now classed in the new number, WL 340.1

Summary of Opiate Overdose Changes

  • The new 2021 Opiate Overdose was added to the index
  • Related maintenance was made to the Classification:
    • The caption at QV 90 was changed from Opium to Opiate alkaloids.
    • Opium Alkaloids was added to the index and classed at QV 90
    • A new number was created for Papaveraceae at QV 766.5.R3
    • The classification of Opium was changed from QV 90 to QV 766.5.R3

Gender Terms added

Gender Equity   HQ 1237 - HQ 1237.5

Gender Role   HQ 1075-1075.5

  • In 2020 MeSH, Gender Role was an Entry Term to Gender Identity (WM 617, etc.)
  • Gender Role (social role) is different from Gender Identity (psychological)

Social Terms added

  • Social Evolution HM 626-631
  • Social Inclusion HM 683
  • Social Interaction

General HM 1111

Adolescent WS 462.5.S6

Child WS 105.5.S6

Other F01 Behavior and Behavior Mechanisms added

  • Test Anxiety

General WM 172

Adolescent WS 462.5.E5

Child WS 105.5.E5

  • Human-Animal Interaction QL 85
    • The existing child term, Bonding, Human-Pet was changed to Human-Animal Bond per MeSH
    • The caption at WM 460.5.B7 was changed from Bonding, Human-Pet to Human-animal bond to match MeSH

Sexual Terms added

  • Sexual Arousal

General WJ 702

Female WP 505

Male WJ 702

  • Sexual Selection QU 520
    • 2007 term Mating Preference, Animal (which has Entry Term Sexual Selection, Animal) was added to index at QL 761 to differentiate
  • Sexual Trauma

A new number was created for Sexual Trauma at WM 187

Psychotherapy Terms added

  • Three new terms treed under Psychotherapy were added to the Index. 3 new corresponding WM 420.5 A-Z class numbers were added to the schedule. 1 class number was modified
  • Logotherapy WM 420.5.L6 (new number)
    • In 2020 MeSH, Logotherapy was Entry Term to Psychotherapy
    • Logotherapy was removed from caption at WM 460.5.E8 (Existentialism. Logotherapy). MS for Logotherapy indicates this is “Directive existential psychotherapy …” but this term does not belong classed in the psychoanalysis area
  • Psychosocial Intervention WM 420.5.P4 (new number)
  • Schema Therapy WM 420.5.S3 (new number). In 2020 MeSH, Schema Therapy was Entry Term to Psychotherapy

Nursing Terms added

  • Developmental Disability Nursing WY 172 (new number)
  • Trauma Nursing WY 154.2
    • Trauma Nursing added to caption with Emergency Nursing

Food Terms added

  • Three new food terms were added to the index classed at WA 695
    • Food Deserts
    • Food Insecurity
    • Food Security
  • WA 695 now allows for geographical breakdown
  • A new number WA 695.1 was added for non-geographic breakdown

Internet Terms

Two new internet terms were added to Index

  • Internet Addiction Disorder

General WM 176

Adolescent WS 462.5.T4

Child WS 105.5.T4

  • Internet Use

Effect on adolescents WS 462.5.T4 

Effect on children WS 105.5.T4

See also Internet Addiction Disorder

Person Terms

Two new index terms from the M tree were added. One new class number was added.  One class number modified

  • Metal Workers WA 487.5.M4 (new number) added
  • Psychotherapists

General WM 21


   Collective WZ 112.5.P7

   Individual WZ 100 

Directories WM 22 

Interpersonal Relations WM 62

  • Psychotherapists was added to the caption at WZ 112.5.P7

Main Index Headings Changes Based on MeSH 2021

For 2021, of the 14 MeSH headings were either changed or deleted and replaced with more up-to-date terminology, only five affected the NLM Classification

Replaced Term

Replaced-By Term

Alaska Natives

Alaskan Natives

Bonding, Human-Pet

Human-Animal Bond

Clostridium difficile

Clostridioides difficile

Mentally Disabled Persons

Persons with Mental Disabilities

Respiratory Distress Syndrome, Adult

Respiratory Distress Syndrome

List of All Class Numbers Added for the 2021 Winter Edition

New Class Number


QV 766.5.R3


QW 40

Microorganisms (General or not elsewhere classified)

QW 46 

Microbial genetics

QW 48   

Blood-borne pathogens

WA 330.1

General coverage (Not Table-G)

WA 487.5.M4

Metal workers

WA 695.1

General coverage (Not Table-G)

WB 142.5

Clinical decision-making

WC 160.5


WC 506               


WC 506.1


WC 506.2


WC 506.3

Etiology. Transmission

WC 506.4

Epidemiology (Table-G)

WC 506.41

General coverage (Not Table-G)

WC 506.5


WC 506.6

Prevention and control

WC 506.7

Psychological aspects.  Socioeconomic factors

WL 340.1

Neurobehavioral manifestations

WM 187

Sexual trauma

WM 413

Complementary therapies (General or not elsewhere classified)

WM 414


WM 416

Mind-body therapies

WM 420.5.L6


WM 420.5.P4

Psychosocial intervention

WM 420.5.S3

Schema therapy

WY 153.7

COVID-19 nursing

WY 172

Developmental Disability Nursing