International Classification of Diseases facts for kids

"ICD" redirects here. For other uses, see ICD (disambiguation).

The International Classification of Diseases (ICD) is a special system used around the world to classify health conditions. Think of it like a big dictionary or a codebook for diseases, injuries, and other health problems. It helps doctors, scientists, and health managers understand and track health information globally.

The World Health Organization (WHO) manages the ICD. The WHO is a part of the United Nations System that focuses on health worldwide. The ICD helps everyone use the same language when talking about health issues. This makes it easier to collect information about diseases, see how they spread, and manage healthcare. Each health condition gets a unique code, which can be up to six characters long. This way, similar diseases are grouped together.

The WHO publishes the ICD. It is used everywhere to collect facts about sickness and deaths. It also helps with how healthcare costs are paid and supports decisions in hospitals. The ICD helps countries compare their health information. It is a main tool for understanding health problems and helping with diagnoses.

The ICD is updated regularly. The newest version is called ICD-11. The WHO approved ICD-11 on May 25, 2019. It officially started being used on January 1, 2022. By February 11, 2022, 35 countries were already using ICD-11.

The ICD is part of a "family" of health classifications from the WHO. Other systems in this family include:

The International Classification of Functioning, Disability and Health (ICF). This system looks at how health conditions affect a person's abilities and daily life.
The International Classification of Health Interventions (ICHI). This system classifies different medical treatments and health actions.

The full name of the ICD is the International Statistical Classification of Diseases and Related Health Problems. But most people just call it the ICD.

In some countries, like the United States, another guide called the Diagnostic and Statistical Manual of Mental Disorders (DSM) is often used for classifying mental health conditions.

How the ICD Started
- Expanding the System
Different Versions of ICD
How ICD is Used in the United States
Mental Health Conditions in ICD
See also

How the ICD Started

The idea for the ICD began a long time ago. In 1860, Florence Nightingale, a famous nurse, suggested a way to collect hospital information. Later, in 1893, a French doctor named Jacques Bertillon created a system to classify causes of death. Many countries started using Bertillon's system.

This system was revised every 10 years to keep up with new medical knowledge. The first international meeting to update it was in 1900. At first, the classification was in one small book.

Expanding the System

The system grew over time. The sixth update, published in 1949, was a big change. It started including information about sickness (morbidity) as well as deaths (mortality). Its name changed to the International Statistical Classification of Diseases, Injuries and Causes of Death.

Before 1948, different groups were in charge of updating the ICD. But in 1948, the WHO took over this important job. The WHO has been responsible for preparing and publishing the ICD updates ever since.

Today, the ICD is the most used system for classifying diseases worldwide. Some countries, like Australia, Canada, and the United States, have made their own versions of the ICD. These versions add more details for medical procedures.

Different Versions of ICD

The ICD has been updated many times to keep it current with medical science. Each new version helps health professionals classify conditions more accurately.

ICD-9

The ninth version of the ICD, called ICD-9, was approved in 1975. It added much more detail than earlier versions. It also offered a special way to classify conditions that involved both a general disease and its effect on a specific body part. This was known as the "dagger and asterisk system."

When ICD-9 was created, another system called the International Classification of Procedures in Medicine (ICPM) was also developed. The ICPM classified medical procedures like surgeries and tests. Many countries used parts of the ICPM.

ICD-9-CM (United States)

In the United States, a special version called the International Classification of Diseases, Clinical Modification (ICD-9-CM) was used. This version added even more details for use in hospitals and doctor's offices. It had three parts: two for diagnosis codes and one for procedure codes. It was updated every year.

ICD-10

Work on ICD-10 began in 1983. This new version was approved in 1990 and started being used in 1993. ICD-10 was a huge step forward. It had over 55,000 different codes, which was a big increase from the 17,000 codes in ICD-9. This allowed for tracking many new diagnoses and procedures.

Most countries quickly started using ICD-10. The WHO provided many online tools and guides to help people use it. Some countries, like Australia and Canada, created their own versions of ICD-10 with extra details.

ICD-10-CM (United States)

The United States was slower to adopt ICD-10. For many years, it continued to use ICD-9-CM for most health claims. However, the US did adopt ICD-10 for reporting causes of death in 1999.

The US created its own clinical versions of ICD-10:

ICD-10-CM: For diagnosis codes, replacing the diagnosis parts of ICD-9-CM.
ICD-10-PCS: For procedure codes, replacing the procedure part of ICD-9-CM.

After several delays, the United States officially started requiring the use of ICD-10-CM for most health records on October 1, 2015.

ICD-10-CM included many improvements:

More details for outpatient care.
Expanded codes for injuries.
New codes that combine a diagnosis and a symptom.
Added sixth and seventh digits for more specific classification.
Codes for left or right side of the body.
More detailed classifications for better data.

ICD-10-CA (Canada)

Canada developed ICD-10-CA. This version is used for classifying sickness in Canada. It includes not only diseases but also things that can affect health, like lifestyle choices.

ICD-11

ICD-11 Beta browser icon

The eleventh version, ICD-11, is much larger than ICD-10. It took over 10 years to develop, with help from more than 300 experts from 55 countries. A stable version was released in June 2018. All WHO members officially approved it in May 2019.

For ICD-11, the WHO decided to create a main "Foundation Component" that holds all ICD information. From this, different versions can be made. The main version, called ICD-11 MMS (Mortality and Morbidity Statistics), is what people usually mean when they say "ICD-11."

ICD-11 comes with many tools to help countries use it. These include ways to switch from ICD-10 to ICD-11, a translation tool, and training materials. All these tools are available online.

ICD-11 officially started on January 1, 2022. However, the WHO knew that not all countries would switch over quickly. In the United States, it is expected that ICD-11 will be adopted in the coming years.

How ICD is Used in the United States

In the United States, different versions of the ICD have been used over time. The US Public Health Service created special versions to meet the needs of hospitals.

The ICD, 9th Revision, Clinical Modification (ICD-9-CM) was widely used by hospitals and other healthcare places. It helped describe a patient's health condition in detail. The diagnosis part of ICD-9-CM was the standard for reporting sickness.

Later, the US moved to ICD-10-CM for diagnoses and ICD-10-PCS for procedures. This change was officially required for most clinical records starting October 1, 2015.

The causes of death in the United States have been classified by different ICD versions over the years:

ICD-1: 1900
ICD-2: 1910
ICD-3: 1921
ICD-4: 1930
ICD-5: 1939
ICD-6: 1949
ICD-7: 1958
ICDA-8: 1968
ICD-9-CM: 1979
ICD-10-CM: 1999

The Centers for Disease Control and Prevention (CDC) uses the ICD to record causes of death on death certificates.

Mental Health Conditions in ICD

The ICD includes sections that classify mental and behavioral health conditions. The ICD-10 Classification of Mental and Behavioural Disorders provides guidelines for diagnosing these conditions. This guide was developed alongside the Diagnostic and Statistical Manual of Mental Disorders (DSM) from the American Psychiatric Association. Both systems aim to classify mental health conditions in similar ways.

A study of doctors in 66 countries found that ICD-10 was often used for diagnosing patients. The DSM was more often used for research.

Experts working on ICD-11 have made sure that the classification of mental, behavioral, and neurodevelopmental disorders is helpful for healthcare. They focus on what helps with health services and treatment.