International Classification of Diseases
The International Classification of Diseases (ICD) is a globally used medical classification used in epidemiology, health management and for clinical purposes. The ICD is maintained by the World Health Organization (WHO), which is the directing and coordinating authority for health within the United Nations System.[1] The ICD is originally designed as a health care classification system, providing a system of diagnostic codes for classifying diseases, including nuanced classifications of a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances, and external causes of injury or disease. This system is designed to map health conditions to corresponding generic categories together with specific variations, assigning for these a designated code, up to six characters long. Thus, major categories are designed to include a set of similar diseases.
"ICD" redirects here. For other uses, see ICD (disambiguation).
The ICD is published by the WHO and used worldwide for morbidity and mortality statistics, reimbursement systems, and automated decision support in health care. This system is designed to promote international comparability in the collection, processing, classification, and presentation of these statistics. The ICD is a major project to statistically classify all health disorders, and provide diagnostic assistance. The ICD is a core statistically based classificatory diagnostic system for health care related issues of the WHO Family of International Classifications (WHO-FIC).[2]
The ICD is revised periodically and is currently in its 11th revision. The ICD-11, as it is therefore known, was accepted by WHO's World Health Assembly (WHA) on 25 May 2019 and officially came into effect on 1 January 2022.[3] On 11 February 2022, the WHO stated that 35 countries were using the ICD-11.[4]
The ICD is part of a "family" of international classifications (WHOFIC) that complement each other, also including the International Classification of Functioning, Disability and Health (ICF) which focuses on the domains of functioning (disability) associated with health conditions, from both medical and social perspectives, and the International Classification of Health Interventions (ICHI) that classifies the whole range of medical, nursing, functioning and public health interventions.
The title of the ICD is formally the International Statistical Classification of Diseases and Related Health Problems, although the original title, International Classification of Diseases, is still informally the name by which it is usually known.
In the United States and some other countries, the Diagnostic and Statistical Manual of Mental Disorders (DSM) is preferred for the classification of mental disorders for some purposes.
Versions of ICD[edit]
ICD-6[edit]
The ICD-6, published in 1949, was the first to be shaped to become suitable for morbidity reporting. Accordingly, the name changed from International List of Causes of Death to International Statistical Classification of Diseases. The combined code section for injuries and their associated accidents was split into two, a chapter for injuries, and a chapter for their external causes. With use for morbidity there was a need for coding mental conditions, and for the first time a section on mental disorders was added .[9][10]
ICD-7[edit]
The International Conference for the Seventh Revision of the International Classification of Diseases was held in Paris under the auspices of WHO in February 1955. In accordance with a recommendation of the WHO Expert Committee on Health Statistics, this revision was limited to essential changes and amendments of errors and inconsistencies.[10]
ICD-8[edit]
The 8th Revision Conference convened by WHO met in Geneva, from 6 to 12 July 1965. This revision was more radical than the Seventh but left unchanged the basic structure of the Classification and the general philosophy of classifying diseases, whenever possible, according to their etiology rather than a particular manifestation. During the years that the Seventh and Eighth Revisions of the ICD were in force, the use of the ICD for indexing hospital medical records increased rapidly and some countries prepared national adaptations which provided the additional detail needed for this application of the ICD.
Mental health conditions[edit]
The various ICD editions include sections that classify mental and behavioural disorders. The ICD-10 Classification of Mental and Behavioural Disorders: Clinical Descriptions and Diagnostic Guidelines – also known as the "blue book" – is derived from Chapter V of ICD-10 and gives the diagnostic criteria for the conditions listed at each category therein. The blue book was developed separately to, but coexists with, the Diagnostic and Statistical Manual of Mental Disorders (DSM) of the American Psychiatric Association—though both seek to use the same diagnostic classifications. A survey of psychiatrists in 66 countries comparing use of the ICD-10 and DSM-IV found that the former was more often used for clinical diagnosis while the latter was more valued for research.[35]
As part of the development of the ICD-11, WHO established an "International Advisory Group" to guide what would become the chapter on "Mental, behavioural or neurodevelopmental disorders".[36][37] The working group proposed that ICD-11 should declassify the categories within ICD-10 at "F66 Psychological and behavioural disorders that are associated with sexual development and orientation".[36][38] The group reported to WHO that there was "no evidence" these classifications were clinically useful, as they do not "contribute to health service delivery or treatment selection nor provide essential information for public health surveillance."[36] Adding that; despite ICD-10 explicitly stating "sexual orientation by itself is not to be considered a disorder", the inclusion of such categories "suggest that mental disorders exist that are uniquely linked to sexual orientation and gender expression." A position already recognised by the DSM, as well as other classification systems.
The ICD is actually the official system for the US, although many mental health professionals do not realize this due to the dominance of the DSM.
A psychologist has stated: "Serious problems with the clinical utility of both the ICD and the DSM are widely acknowledged."[39]
Note: Since adoption of ICD-10 CM in the US, several online tools have been mushrooming. They all refer to that particular modification and thus are not linked here.