From ILCD to ICD-10

The following notes on the history and development of ICD are largely taken from the "Introduction to the international classification of diseases, injuries and causes of death" in Volume 1 of the ICD-7 handbook which describes in detail the beginnings of disease classifications. Many of the details mentioned there are also included in the "History of the development of ICD", included as Chapter 6 of Volume 2 (Instruction manual) of the handbook for ICD-10 of WHO.

These documents on the early revision do not speak of "codes" and "encoding" but of "position numbers" and "signing". For a better understanding, note the different aims of nomenclatures and classifications. An unofficial overview of the revisions of the English-language version makes it possible to compare structures.

• Nomenclatures and Classificationen (in German language)
• From BCCD over ILCD to ICD-10 at Wolfbane Cybernetic Ltd

Pioneers in the classification of diseases

The first systematic classifications of diseases date back to the early 18th century.

• Francois Bossier de Lacroix ("Sauvages") (1706-1777): Nosologia Methodica
• Carl von Linné ("Linnaeus") (1707-1778): Genera morborum
• William Cullen (1710-1790): Synopsis Nosologiae Methodicae

At the start of the 19th century, the classification most used was Cullen’s Synopsis Nosologiae Methodicae; however, since its first publication, it was neither updated in line with medical progress nor did it seem suitable for statistical purposes.

Pioneers of health statistics

In 1593, baptisms and burials were first recorded in England for the London area. These London Bills of Mortality were continued until 1837. Their purpose was the early identification of increased incidences of deaths from plague or other such epidemics. In 1836, they were replaced by the Registrar General's Returns in accordance with the Births and Deaths Registrations Act. 1837 saw the establishment of the General Register Office (GRO) for England and Wales.

• John Graunt (1620-1674): published his Natural and Political Observations Made upon the Bills of Mortality in 1662.
• Dr. William Farr (1807-1883): first medical statistician of the General Register Office for England and Wales; in 1839, he published an analysis of the causes of death based on the registration of the causes of death in England and Wales from July to December 1837.
• Dr. Jacob Marc d'Espine (1806-1860): member of the Societe Medicale d'Observation in Paris, an organisation dedicated to the numerical analysis of diseases; in 1840, he published a study of 1323 deaths in the Swiss Canton of Geneva in 1838.
• Lambert Adolphe Jacques Quetelet (1796-1874): studied statistics of social phenomena and was one of the most influential statisticians of the 19th century. He was the initiator and president of the first International Statistical Congress in Brussels in 1853.
• Dr. Jaques Bertillon (1851-1922): Director of the Municipal Office of Statistics in Paris and author of the Bertillon Classification of Causes of Death.
• Florence Nightingale (1820-1910): introduced statistical principles to nursing and demanded the use of disease registers for hospital statistics.

From a register of the causes of death to a classification of diseases, injuries and causes of death

The history of ICD is characterised by a series of revision conferences numbered from 1 to 10. In this context, it is to be noted that the revision conferences 1 to 5 refer to the register of the causes of death (ILCD), while the later conferences 6 to 10 refer to the ICD classification.

Until the Fourth Revision conference of the International List of Causes of Death (ILCD), registers of diseases and registers of causes of death are seen as completely different and entirely separate:

• Registers of causes of death are lists of diseases leading to death.
• Registers of diseases are lists of diseases not leading to death but impairing health.

A rethink of this approach started with the Fifth Revision Conference and the "United States Committee on Joint Causes of Death", established in 1945 in the wake of that conference. Its remit was to study "competing" causes of death, i.e. the question of selecting the main cause of death for death certificates if several causes of death are mentioned. The committee recognises that registers of causes of death and registers of diseases should not merely be compatible - as recommended by the Fifth Revision Conference - but that there should be a common register for diseases and deaths.

The Sixth Revision Conference then adopted the International Statistical Classification of Diseases and Related Health Problems (ICD)

Development of the International List of Causes of Death (ILCD)

1853 First International Statistical Congress, Brussels
Statistics pioneers Farr and d'Espine meet at the first International Statistical Congress in Brussels. The congress passes a resolution on the urgent need of a standardised international nomenclature of causes of death. Farr and d'Espine are tasked with its development.

1855 Second International Statistical Congress, Paris
Farr and d'Espine submitted two separate lists of the causes of death.
Farr’s system was arranged under 5 groups of diseases: epidemic diseases, constitutional (general) diseases, local diseases arranged according to anatomical site, developmental diseases, and diseases as the direct result of violence.
D'Espine classified diseases according to their nature (gouty, herpetic, haematic, etc.). As a compromise between the views of Farr and d'Espine, the congress adopted a compromise list of 139 groups of diseases.

1864
The compromise system of 1855 is revised and published "sur le modèle de celle de W. Farr", i.e. in accordance with Farr's model, with its main principle: the classification by anatomical site. 1874, 1880 and 1886 saw further improvements to the system. Though never universally accepted, it became the basis of the International List of Causes of Death.

1891 International Statistical Institute, Vienna
The International Statistical Institute (successor to the International Statistical Congress) at its meeting in Vienna charged a committee chaired by Bertillon with the preparation of a systematic classification of causes of death.

1893 International Statistical Institute, Chicago
Bertillon presented his classification at the meeting of the International Statistical Institute in Chicago. It was based on the classification of causes of death used by the City of Paris which since its revision in 1885 represented a synthesis of English, German and Swiss classifications. The classification was based on Farr's principle of distinguishing between general diseases and those localised to a particular organ. Bertillon included three classifications: an abridged classification of 44 titles, a second with 99 and a third with 161 titles (or codes). The Bertillon Classification of Causes of Death (BCCD) received general approval as the International List of Causes of Death (ILCD). It was adopted by all statistical offices in North America.

1899 International Statistical Institute, Oslo
At the meeting of the International Statistical Institute in Oslo, European statistical offices are urgently recommended to use the Bertillon Classification; the decision is made to hold a revision conference every ten years to check and improve the classification.

1900 First International Conference for the Revision of the Bertillon or International List of Causes of Death (ILCD), Paris (First Revision Conference)
The First International Revision Conference adopted a detailed classification consisting of 179 groups and an abridged classification of 35 groups.

1902 Second ILCD Revision Conference, Paris

1920 League of Nations
The League of Nations was founded and appointed a statistical committee whose remit included the classification of diseases and causes of death.

1920 Third ILCD Revision Conference, Paris

1923
Michel Huber succeeds Bertillon at the International Statistical Institute. He introduced a resolution to cooperate with other international organisations in the revision of the classification of causes of death. To coordinate the works of the International Statistical Institute on the one hand and the Commission of Statistical Experts of the League of Nations on the other, an international commission with an equal number of representatives of both organisations was created, known as the Mixed Commission. This commission drafted the proposals for the Fourth and Fifth Revision Conferences.

1928 Roesle monograph on the expansion of the list of causes of death
The Health Organisation of the League of Nations published a monograph by Dr Roesle, Chief of the German Health Bureau and a member of the Commission of Expert Statisticians. Dr Roesle's paper listed the expansion of the groups in the 1920 International List of Causes of Death (Third Revision) that would be required if it was to be used in the tabulation of statistics of morbidity.

1929 Fourth ILCD Revision Conference, Paris

Development of classifications of diseases

The First, Second and Third Revision Conferences of the Bertillon List of Causes of Death, a statistical list of diseases was approved in parallel to the list of causes of death. However, these attempts at an international classification of diseases were not introduced on a general basis because they were little more than limited extensions of the list of causes of death.

1938 Fifth ILCD Revision Conference, Paris
The Fifth Revision Conference approved three lists: a detailed list of 200 titles, an intermediate list of 87 titles and an abridged list of 44 titles.

Canadian delegates presented a modified version of a list of diseases ("Standard Morbidity Code" published in 1936 by the Dominion Council of Health of Canada; in its subdivisions, it corresponds to the International List of Causes of Death of 1929. They suggested this list as the basis for an International List of Diseases, but the proposal is not debated.

However, in its resolution, the conference stressed the importance of a classification of diseases in line with the list of causes of death, and recommended that the International Statistical Institute and the League of Nations, represented by the Mixed Committee, should draft an international list of diseases in cooperation with other interested organisations and experts. For the meantime, the conference recommended as far as possible to bring into line the various national lists of diseases then in use with the detailed international list of causes of death.

A further resolution concerned the problem of selecting the primary cause of death if the death certificate stated several joint causes of death. This problem had been the subject of lengthy study particularly in the United States, but without arriving at a solution. The conference recommended to the US government to appoint a committee to focus on this problem.

1945 United States Committee on Joint Causes of Death
In compliance with the resolution of the Fifth Revision Conference, the "United States Commitee on Joint Causes of Death" was appointed to take up the matter of joint causes of death. In addition to the US government, members of this committee also included representatives from Canada and the UK as well as from the Health Organisation of the League of Nations.

The committee recognised the close link between the problem of joint causes of death and the list of causes of death (fatal diseases) on the one hand and the list of diseases (non-fatal diseases) on the other. For that reason, the classification of causes of diseases and of disease should not just be comparable - as recommended by the Fifth Revision Conference - , but ideally combined in a single list. A single list would make classification much easier and because of the shared basis would result in comparable morbidity and mortality statistics. A subcommittee presented a draft of a Proposed Statistical Classification of Diseases, Injuries and Causes of Death; the draft was adopted by the Committee on Joint Causes of Death after it had been modified on the basis of field trials.

International Classification of Diseases, Injuries and Causes of Death: ICD

1946 International Health Conference, New York
The Interim Commission of the World Health Organisation WHO (the WHO was only established in 1948) is charged with conducting the Sixth Revision Conference for the International List of Causes of Death and compiling an International List of the Causes of Disease. To this end, the "Expert Committee for the Preparation of the Sixth Decennial Revision of the International Lists of Diseases and Causes of Death" was appointed.

On the basis of a proposed draft by the United States Committee on Joint Causes of Death, the Expert Committee developed an international classification of diseases, injuries and causes of death as well as an associated alphabetical index of all disease names included in the classification.

1948 International Conference on the Sixth Revision of the International List of Diseases and Causes of Death, Paris
The Conference adopts the International Classification of Diseases, Injuries and Causes of Death developed by the Expert Committee: ICD-6 of the WHO was born. In addition, the conference recommended an extensive programme for the international cooperation with regard to population and health statistics. This led to the formation of national committees for population and health statistics and international cooperation under the coordination of the WHO Expert Committee on Health Statistics.
ICD-6

1951 WHO Centre for the Classification of Diseases
On the recommendation of the WHO Expert Committee on Health Statistics, the WHO Centre for the Classification of Diseases was set up in the General Register Office for England and Wales in 1951. It promoted the use of ICD-6 and supported users with correspondence and brochures, such as an Addendum to ICD-6 entitled "Supplementary Interpretations and Instructions for Coding Causes of Death". In addition, the Centre supported the preparations for the Seventh Revision Conference scheduled for 1955 which was to be restricted to the amendment of errors and inconsistencies.

1955 Seventh ICD Revision Conference, Paris
The Seventh Revision was limited to essential changes and the amendment of errors and inconsistencies. The structure of ICD-7 remains the same as for ICD-6, the number and structure of the published classifications (Tabular List of inclusions and four-character subcategories (VAS), Tabular List of three-character categories index (DAS), lists A, B, C and Alphabetical Index) are identical.

1965 Eighth ICD Revision Conference, Geneva
The Eighth Revision was a bit more radical than the Seventh but left unchanged the basic structure and the general principle of classification of diseases by preference according to their aetiology. Together with ICD-8, two special tabulation lists were also approved: List D with 300 causes for the tabulation of hospital mortality and List C with 100 causes for the tabulation of perinatal morbidity and mortality.
ICD-8

1975 Ninth ICD Revision Conference, Geneva
While maintaining the same basic structure, ICD-9 contains numerous new details on the level of the four-character subgroups/subcategories; in various places, optional five-character subdivisions became possible. In addition, the dagger-and-asterisk system was introduced, permitting the classification of the manifestation of a disease in a certain organ system together with the underlying general disease in form of a double classification. Furthermore, the 5 special tabulation lists of ICD-8 were replaced by 3 new special tabulation lists: a basic systematic index, a very brief list of causes of death and a very brief list of diseases. Also part of ICD-9 are two separate systematic indexes, the E-classification (External causes of injuries and poisonings) and the V-classification (Factors influencing health status and contact with health services).
ICD-9

1989 Tenth ICD Revision Conference, Geneva
The Tenth Revision has been considerably extended compared to ICD-9. The additional classifications E and V of ICD-9 were integrated. Encoding, up to this point entirely numeric, was replaced with an alphanumeric code which permits expansion
ICD-10-WHO