The background of ICD-9 codes--which stands for the International Classification of Diseases, 9th Version--was to be able to track how people died. Later on, ICD codes were used to track diseases and injuries to find patterns that might show an epidemic could be coming, as well as to track the general health of people. These days, ICD-9 codes are not only used for this purpose, but for medical billing in the U.S.
Early History of ICD Codes
Back in the 1700s, the first attempt at classifying diseases was made by a French physician, François Boissier de Sauvages de Lacroix, who wrote the first book on the subject "Nosologia Methodica." Many different physicians followed up on his process, upgrading it to better reflect diseases as more were discovered.
In 1853, at the first International Statistical Congress in Paris, it was agreed that there should be a uniform classification of diseases for the world to use. In 1855, the first standards for classification were introduced, and from that point on, there was an outline for how the coding process should work.
Diseases and Injuries
For the next 95 years, there were multiple revisions and changes to the code, but no universal agreement on the standards. Many countries developed their own coding system, although all used the bases that were already established in categorizing these diseases.
In 1938, Canada introduced a proposal for the listing of causes of diseases. The Fifth International Congress adopted the ruling although there was no formal action taken on it. By 1944, there was a provisional list of diseases and injuries, presented by the U.S. and the United Kingdom.
Universal Agreement
It wasn't until 1948, just after the creation of the World Health Organization, that there was a committee put together to establish one revision to represent all countries. The idea was to put together not only a classification of causes of death, but also classifications of illnesses and injuries. This became known as the Sixth Revision of the International Lists. The committee created the "Manual of the International Statistical Classification of Diseases, Injuries, and Causes of Death" from the data, which was in two volumes. By the time of the 7th revision, in 1955, the name International Classification of Diseases had been adopted.
ICD 9th Version Adoption
The 9th version of ICD came about in 1977. To date, it's the last version that every country adopted at the same time. Incorporated into it were many of the category extensions of diseases and maladies that several represented countries wanted for better clarity of what was occurring in their areas.
The next update for ICD was supposed to begin in 1985, following what had become a 10-year process for working on ICD codes. However, it was pushed back to 1989, and continuing delays kept it from coming out until 1995.
Why ICD-9 Remains
While most of the world has switched to ICD-10, the U.S. has remained on the current system because of billing and payment issues. In 1983, ICD-9 was introduced as being a critical part of medical billing by physicians and hospitals, and was further embedded by the passage of the Medicare Catastrophic Coverage Act.
That act was later repealed, but the payment process was already set, as other insurance companies adopted the same standards. At this point, the U.S. is expected to change over to the ICD-10 system by 2011, but the actual date hasn't been formally given.
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