Frequently Asked Questions


Q:  What is the International Classification of Diseases (ICD)?

A:  It is a classification system developed and maintained by the World Health Organization (WHO). The WHO is the directing and coordinating authority for health within the United Nations system and is chiefly responsible for providing leadership on global health matters, setting standards, providing technical support to countries and monitoring health trends. The ICD is an international standard diagnostic classification system providing the basis for national morbidity and mortality statistical data collection to improve the management of healthcare. It is used to classify diseases and other health conditions that are documented on various types of medical records. Over the years, the use of the ICD for indexing hospital medical records increased rapidly and some countries have prepared national adaptations which provide the additional detail needed for a specific application of the ICD.


Q:  What classification system do other countries use for medical coding?

A:  Most of the rest of the world is using ICD-10 or a clinical modification of ICD-10. The US is the only industrialized nation not using an ICD-10-based classification system for morbidity reporting.


Q:  Why does it matter if the rest of the world is moving to ICD-10?

A:  If we do not adopt ICD-10, we will not have compatible data to compare internationally. As many other countries have already moved to ICD-10, we will be capturing morbidity data using the outdated classification system, ICD-9-CM. This has already led to problems identifying and tracking new health threats. It will severely limit our ability to compare outcomes of new technologies used in the U.S. and abroad. It will also limit our ability for surveillance and to develop and quickly respond to interventions for emerging diseases. We are a global community, it is vital that our health care data represent current medical conditions and technologies and that it is compatible with the international version of ICD-10. Some of these are:

Example: Identifying and tracking diseases impacted by Anthrax, Severe Acute Respiratory Syndrome (SARS), and Monkeypox are increasingly important in our global community.

Example: Since the U.S. moved to using ICD-10 for coding mortality data (for death certificates) in 1999, state specific mortality data (ICD-10) cannot be easily compared to hospital morbidity data (ICD-9-CM) to track this with leading causes of death. Additional information on mortality data is available at


Q:  Why is ICD-9 being replaced?

A:  Developed in the 1970s, the ICD-9-CM coding system no longer fits with the 21st century healthcare system. ICD-9-CM is used for many more purposes today than when it was originally developed and is no longer able to support current health information needs.

The US is virtually the only industrial nation that has not upgraded its morbidity classification system. Upgrading to ICD-10-CM/PCS will improve the United States' ability to track and respond to international public health threats, increase the value of the US investment in SNOMED-CT®, and better achieve the benefits of an electronic health record.

Specifically, ICD-9-CM:

  • Lacks sufficient specificity and detail
  • Is running out of capacity, and the limited structural design cannot accommodate advances in medicine and medical technology and the growing need for quality data
  • Is obsolete and no longer reflects current knowledge of disease processes, contemporary medical terminology, or the modern practice of medicine
  • Hampers the ability to compare costs and outcomes of different medical technologies
  • Cannot support the US transition to an interoperable health data exchange in the US

Replacing ICD-9-CM with ICD-10-CM will better maintain clinical data comparability with the rest of the world concerning the conditions prompting healthcare services. ICD-10-CM will make it easier to share disease and mortality data at the time when such global data sharing is critical for public health. For example:

  • ICD-10-CM would have better documented the West Nile Virus and SARS complexes for earlier detection and better tracking
  • ICD-10-CM also provides the ability to track bio-terrorism events and other public health outbreaks

The need to replace ICD-9-CM was identified in 1993, when the National Committee on Vital and Health Statistics (NCVHS) reported that ICD-9-CM was rapidly becoming outdated and recommended immediate US commitment to developing a migration to ICD-10-CM for morbidity and mortality coding. Similarly, the Health Care Financing Administration (HCFA), now the Centers for Medicare and Medicaid Services (CMS), recommended that steps should be taken to improve the flexibility of ICD-9-CM or replace it with a more flexible option sometime after the year 2000.



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