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ICD-9-CM Code Set

The International Classification of Diseases (ICD) is the oldest method of tracking diseases and mortality in the world. It was developed in Europe, and several versions have evolved over the years. The first edition, known as the International List of Causes of Death, was adopted by the International Statistical Institute in 1893. The current version used in the United States was established by the World Health Organization (WHO) and has seen regular modifications. ICD-9-CM (Clinically Modified) was adopted in this country in 1979. The code set is updated at least once a year, based on the input of providers, payers, and other key stakeholders. A new generation and much larger code set, ICD-10, will replace ICD-9 codes on October 1, 2015.

Already the standard for diagnostic and inpatient hospital coding in the United States, ICD-9-CM was mandated in 2003 by the Health Insurance Portability and Accountability Act of 1996 (HIPAA). A comprehensive understanding of the ICD-9-CM code set is essential for all medical coders and billers who work for health plans, healthcare clearinghouses, and healthcare providers that transmit any electronic health information.

The ICD-9-CM code set consists of:

  • Volume 1: The numeric listing of diseases, classified by etiology and anatomical system, along with as a classification of other reasons for encounters and causes of injury. This is called the tabular section of ICD-9-CM. Volume 1 is used by all health care providers and facilities.
  • Volume 2: The alphabetic index used to locate the codes in Volume 1. Volume 2 is used by all health care providers and facilities.
  • Volume 3: A procedural classification with a tabular section and an index. This set of procedure codes is used only by hospitals to report services.

All ICD-9-CM changes and modifications are the responsibility of the Centers for Disease Control (CDC), the National Center for Health Statistics (NCHS), and the Centers for Medicare & Medicaid Services (CMS).

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