An Overview of the ICD-9-CM Process

April 2, 2009


By Laura B. Powers, MD, FAAN

The International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM), is the diagnostic classification system used in the United States for morbidity reporting and for reporting medical necessity for services claimed for reimbursement. The "Clinical Modification," developed mainly for use in the United States, is an expansion used by only a few countries; most other countries currently use ICD-10 for morbidity reporting. The United States uses ICD-10 for mortality reporting on death certificates. Recently the Department of Health and Human Services (HHS) determined that ICD-10-CM will be implemented in the United States on October 1, 2013, for morbidity and medical necessity reporting.

The World Health Organization has jurisdiction over development and changes in the International Classification of Diseases. In the United States, the National Center for Health Statistics (NCHS), a branch of the Centers for Disease Control and Prevention (CDC), and Centers for Medicare and Medicaid Services (CMS) jointly oversee changes to ICD-9-CM. NCHS coordinates requests for changes in diagnosis coding, and CMS coordinates requests for changes in ICD-9-CM Coding for Procedures (Volume 3), which is used only by hospitals.

Although anyone may request a change to diagnosis codes, most requests come from medical specialty organizations. The requests must comply with the conventions of the classification system, and there must be room in this already nearly full system. The request is submitted to NCHS and, if accepted, is placed on the agenda for the ICD-9-CM Coordination and Maintenance Committee, which meets twice yearly. At that meeting, the proposed change is presented, often by the requester. Comments are accepted during and after the meeting from coding and medical experts. NCHS and CMS make the final decisions about these coding changes in accordance with WHO, and the changes are announced, usually in June, to become effective on October 1.

The American Academy of Neurology Professional Association is represented in the ICD-9-CM Coordination and Maintenance Committee through a physician advisor who is a member of the Coding Subcommittee of the Medical Economics and Management Committee. Ideas for coding changes may come from individual members or from sections. Often the Academy's ICD-9-CM Advisor is contacted by NCHS regarding neurologic coding changes requested by persons or organizations outside the Academy. Where appropriate, the sections are asked to review some of the requested changes through their section coding and reimbursement representative.

Please address questions about ICD-9-CM coding or requests for coding changes to Gina Gjorvad, Medical Economics Administrator, at

Additional ICD-9 Resources

Author Disclosure

Within the past 24 months, Dr. Powers has served as an expert witness or consultant in three separate court cases.