The World Health Organization International Classification of
Diseases (ICD)
The fields of health terminology, classification, ontology, and related
information models have evolved dramatically over the last 25 years (1)
and the increasing demands and uses of information has also transformed
the process of coding. A standard registry of morbidity and mortality
data provides health information for statistics and epidemiology, health
care management, allocation of resources, monitoring and evaluation of
research, and for disease prevention and treatment. This information
need has given rise to a process of coding, whereby words describing
medical conditions are translated into codes (2).
The International Classification of Diseases (ICD) is maintained by the
World Health Organization (WHO) and provides a common language for use
worldwide as a diagnostic and classification tool for epidemiology,
clinical purposes and health management. It enables the analysis of the
general health situation of different population groups and provides
data on the key problems to be managed. It is used to classify diseases
registries for many types of health and administrative purposes
including death certificates and electronic health care records. In
addition to enabling the storage and retrieval of diagnostic information
for clinical, epidemiological and quality purposes, including the needs
of payers and Health Technology Assessment bodies, these reported data
also provide the basis for compilation of national mortality and
morbidity statistics (MMS) by WHO Member States (2,3).
The first edition of the ICD was published in 1893 (4). This
classification distinguished between systemic diseases and those
localized to a particular organ or anatomical site (5). The ICD has thus
far maintained a similar framework, distributing conditions according to
topography (5), with the result that some complex conditions, such as
allergies including anaphylaxis, have been poorly represented.
The ICD has been periodically revised, with most countries now using the
tenth revision (ICD-10) or national adaptations thereof (3). It is used
by more than 100 countries, is available in 43 different languages and
is the tool used for allocating about 70% of the world’s health
expenditure. In the US alone this amounted in 2017 to USD $ 3.5
trillions according to the National Center for Health Statistics (6-8).
Therefore, modification of the ICD framework has the potential to have
an impact on health financing and economics. On the other hand, the
misclassification or underrepresentation of specific disorders in this
global classification system can lead to lack of visibility, investment
and public health action, as proved for allergic and hypersensitivity
conditions (9,10).