Understanding ICD Codes: A Comprehensive Guide

ICD codes are part of an internationally recognized system for describing diseases, symptoms and medical conditions. The most recent version allows more than 12,000 codes.

Administration

• ICD stands for "International Classification of Diseases." The system is maintained by the World Health Organization of the United Nations.

Significance

• Standardizing the identification of diseases and conditions allows for better comparison of health statistics among countries and better coordination of public health efforts.

Systems

• The most recent version of the system is ICD-10. It allows for about twice as many codes as its predecessor, ICD-9, which had been running out of codes. Most countries use only ICD-10; the United States uses both.

In the U.S.

• The U.S. health-care system uses ICD-9 for classifying "morbidity"--diseases and conditions in living people--and ICD-10 for classifying "mortality"--cause of death. The federal government has required ICD-9 codes on all Medicare and Medicaid claims, which has hampered adoption of ICD-10.

Differences

• The ICD-9 system allows for up to five digits, all of them numerals, while ICD-10 allows for up to six characters, the first of which is a letter. The systems' codes are radically different. An asthma attack, for example, is "493.92" in ICD-9, but in ICD-10, it could be "J45.21," "J45.41" or "J45.51," depending on severity.

Identification

• See the links in the Resources section for searchable databases of ICD codes.