Understanding ICD-10 Codes

The World Health Organization’s ICD (International Classification of Diseases and Related Health Problems), from which ICD-9-CM and ICD-10-CM are derived, is the international standard diagnostic classification for all general epidemiological and many health management purposes. The system consists of diagnosis codes used to classify diseases and other health problems recorded on many types of health and vital records including death certificates and patient medical records. In addition to enabling the storage and retrieval of diagnostic information for clinical and epidemiological purposes, these records also provide the basis for the compilation of national mortality and morbidity statistics by World Health Organization (WHO) Member States.

The development of WHO’s ICD-10 code system was based on the realization that the great expansion in the use of the ICD necessitated a thorough rethinking of its structure and an effort to devise a stable and flexible classification that would not require fundamental revision for many years to come.

ICD-10-CM is a US clinical modification of the WHO’s ICD-10 and is maintained by the National Center for Health Statistics (NCHS). It is a morbidity classification system that classifies diagnoses and other reasons for healthcare encounters. The diagnosis code structure is alphanumeric, with codes comprised of 3-7 characters.

ICD-10-PCS is a procedural coding system developed under contract by the Center for Medicare & Medicaid Services (CMS) as a replacement of the ICD-9-CM procedural coding system for hospital reporting of inpatient procedures. It has a 7-character alphanumeric code structure.

The US is the only developed country that has not yet implemented ICD-10 codes (or a clinical modification) for morbidity, meaning diseases or causes of illness typically coded in a healthcare facility. Since 1999, however, the US has used ICD-10 only for mortality reporting—the coding of death certificates (typically done by a vital statistics office, not the healthcare facility). Implementing ICD-10-CM will maintain data comparability internationally and between mortality and morbidity data in the US.

Learn More About ICD-10 diagnosis codes and ICD-10-PCS procedure codes

• AHIMA's Education & Training
• “ICD-10-CM Primer” (May 2008)
• “Why ICD-10 Is Worth the Trouble” (March 2008)
  
• “Brushing up on ICD-10-PCS” (March 2008)
  
• “Effectiveness of ICD-10-CM in Capturing Public Health Diseases” (June 2007)
  
• "Family of International Classifications: Definition, Scope, and Purpose” (August 2004)
  
• "Keeping Classification in the Family: WHO Framework Assigns Systems Based on Numerous Factors" (September 2004)
  
• “ICD-10: All in the Family" (November/December 2004)
  
• "Brief History of ICD-10-PCS" (October 1999)
  
• Centers for Medicare & Medicaid Services
  
• National Center for Health Statistics

Examples

Looking for good examples of converting physician office forms from ICD-9-CM to ICD-10-CM? View two samples of physician superbills:
Example 1
Example 2