Depending on the symptoms, the etiologies, the locations or even the severity… on which criterion (s) is it judicious to classify the diseases? Such is the stake of nosography which, for centuries, preoccupied a great number of scientists. Today, the International Classification of Diseases (ICD) has become the benchmark classification system. Explanations.

Nosography refers to the methodical classification accompanied by a description of the diseases. It is the application of nosology which determines the criteria used for this classification of the various pathologies. Indeed, these criteria can be semiological (depending on the symptoms), etiological (depending on the causes) or even pathogenic (depending on the types of pathogenic agents and their mechanisms). Once the criterion has been determined, the classification can be made.

Scientists have tried to classify diseases since the dawn of time.

Antiquity

The first classification of diseases appears in a poem by Pindar (a lyric poet of the fifth century BC). The criterion used is then that of the endogenous or exogenous origin of the disease: Pindar distinguishes between diseases linked to a factor external to the body (trauma, seasonal illnesses, etc.) and diseases which appear in the body1. We find this classification in the Hippocratic Treatise.

Other classification criteria appear: according to the region of the body affected², according to the number of individuals affected at the same place / time (epidemic diseases / sporadic diseases), according to the severity of the diseases (benign / malignant, curable / incurable)³… Criteria are presented in the works of Galien, Arétée and Soranos³.

The Middle Age

For doctors in the Middle Ages, illness was partly the result of moral disorder. For the “nominalists”, the disease does not exist: there are only patients. For the “realists”, diseases exist and manifest themselves in the sick. The “realistic” thesis ends up imposing itself, which makes new noso necessary.spellings⁴.

The Modern Age

In the 5th century, the doctor Jean Fernel described a bipartite nosography distinguishing the diseases which affect the whole organism and those which affect only one and only one organ. General diseases are subdivided into groups of symptoms while diseases localized to a single organ are classified according to their anatomical locationXNUMX.

Guillaume le Baillou, one of the founders of modern epidemiology (a scientific discipline which studies the distribution of diseases in populations, space and time) writes disease ephemeris (observation of diseases in the same place and geographic space5.

In the 6th century, the English physician Thomas Sydenham evoked the need for a classification of diseases “by species in the manner of botanists” XNUMX.

Modern period

The Swedish naturalist Linnaeus classifies living things and fails in his attempt to apply his system to disease7,8.

The botanist and physician, Boissier De Sauvages is the first to propose a coherent nosology: the Nosologie Methodica (1763). De Sauvages classifies diseases according to semiological criteria (by symptoms). If his system is the starting point for all subsequent systems, he will continue to be criticized for its jargon and disorderly nature9.

In 1776, the Slovenian doctor Jean Michel Sagar also wrote a nosograph based on the observation of symptoms: Symptomatic system diseases⁶.

Thereafter nosologies employ new classification criteria. This is particularly the case of the Philosophical nosography (1798) written by the French doctor Philippe Pinel who uses semiological, physiological and pathological criteria. In 1829, the dermatologist Alibert proposed a “genealogical tree of dermatoses”⁷. The doctor René Laennec, takes up the ideas of Xavier Bichat after his death: the latter distinguished between organic diseases (with detectable tissue damage) and nervous diseases (without observable lesions). Subsequently, the surgeon and pathologist Jean Lobstein in turn proposed a distribution of diseases according to anatomical and semiological criteria.

Towards an international classification of diseases

Doctors William Farr et Marc d’Espine elaborate the very first international classification of diseases which uses anatomical criteria. This was adopted in 1855 by the first international congress of statistics (ISC). This classification becomes a real reference towards the end of the XIX^th century when the ISC (International Statistical Congress) became the ISI (International Statistical Institute).

The French statistician and demographer Jacques Bertillon wrote the International Nomenclature of Causes of Death (Bertillon Classification) which was then adopted by the Chicago conference encouraging the use of this nosography by member countries for statistical purposes. After a first revision, this nomenclature is distributed all over the world. The Bertillon Classification underwent five decennial revisions until 1938.

When the WHO was created in 1945, it was entrusted with the development and updating of the Bertillon Classification. In 1948, the sixth revision became the International Statistical Classification of Diseases, Injuries and Causes of Death: it ceased to list only the causes of death to focus more generally on morbidity.

In 1948, the WHO adopted the International Statistical Classification of Diseases or ICD. The ICD was designed to “allow systematic analysis, interpretation and comparison of mortality and morbidity data collected in different countries or regions at different times”. The ICD assigns listed diseases an alphanumeric code of three to five characters. It is the reference nosography used internationally.

In 1993, the tenth revision of the CIM is carried out: it is the CIM-10. Work on the development of this revision – currently in use – began in 1983 and was completed in 1992. ICD 10 contains approximately 12 codes and has been published in three volumes:

• Volume 1: Analytical table containing 3 and 4 character classification, classification of tumor morphology, special lists for tabulation for mortality and morbidity, definitions and regulation.
• Volume 2: instruction manual for coding, especially in mortality. Notes on certification, classification and tabulation.
• Volume 3: alphabetical index. This index is the essential entry of the classification. Common and less common disease terms are listed there and associated with the ICD 10 code. CIM 10.

ICD-10 will soon be replaced by ICD-11 which was presented to the World Health Assembly in May 2019 for adoption by Member States, and which will enter into force on 1^er January 2022.