ICD9

ICD-9 refers to the ninth revision of the International Classification of Diseases, a standardized system for coding diseases, symptoms, abnormal findings, injuries, and procedures. It was developed by the World Health Organization and became the basis for health statistics and information systems worldwide. In the United States, a clinical modification known as ICD-9-CM was developed to expand the classification for clinical use and to support more detailed medical billing codes. ICD-9-CM includes diagnosis codes and procedure codes; diagnosis codes are typically three to five digits, with a decimal point separating the category and subcategory. Additional external cause and status codes (V and E codes) were used in the classification; procedure codes were introduced to document surgical and other medical interventions.

Historically, ICD-9 was widely used from the 1980s through the 1990s and into the early 2000s, but it was gradually superseded by ICD-10 and ICD-10-CM/PCS in many countries. In the United States, ICD-10-CM for diagnoses and ICD-10-PCS for procedures became effective in 2015, replacing ICD-9-CM. Other countries transitioned to ICD-10 at different times. ICD-9 remains important for historical data, research, and transition documentation. The coding system enables standardized morbidity and mortality statistics, health insurance billing, and clinical research by providing uniform terminology and code sets that map to diseases, symptoms, etiology, and procedures.