The Origins of ICD-10 Coding
The roots of ICD-10 coding go back to the 1850s. The first edition, known as the International List of Causes of Death, was adopted by the International Statistical Institute in 1893.
WHO assumed oversight of the International Classification of Diseases (ICD) in 1948 with the main intention of tracking—and helping to eliminate—diseases within various populations. At the time, the Sixth Revision, which introduced causes of morbidity to the system, had just been published.
In 1957 and 1968, WHO released ICD-7 and ICD-8, respectively. Shortly after the release of ICD-9 in 1979, the US created its own version, known as the International Classification of Diseases, Ninth Revision, Clinical Modification—or, ICD-9-CM.
The development of ICD-9-CM was a tremendous boon. Not only did the new system expand the ability to capture enhanced morbidity data, but it also incorporated surgical procedures and other items necessary to categorize the needs of hospitals.
But ICD-9-CM, updated annually by CMS and the NCHS, was a limited system with a limited capacity for the addition of codes to keep pace with modern healthcare. And it was already a three-volume set, with the first two volumes dedicated to diagnosis codes and the third volume containing inpatient procedural codes.
So, after decades in the making, CMS and NCHS adopted ICD-10 and adapted the classification to create a new version, the International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM), which no longer included the third volume of inpatient procedure codes.
What happened to the inpatient procedure codes? CMS determined the need for better organization and funded a project with 3M Health Information Systems in 1995 to develop the International Classification of Diseases, Tenth Revision, Procedure Coding System (ICD-10-PCS).
The Difference Between ICD-10-CM & ICD-10-PCS
Both ICD-10-CM and ICD-10-PCS came into effect for medical claims reporting on Oct.1, 2015. But the two code sets differ vastly. The primary distinctions are:
- ICD-10-CM—diagnosis code set used for all healthcare settings
- ICD-10-PCS—procedure code set used only in hospital inpatient settings
The terms ICD-10-CM and ICD-10 are used interchangeably in the US. This linguistic trend underscores the distinction between CM and PCS, in that ICD-10-CM is ubiquitous across healthcare settings, used by every medical coder as the singular means to report diagnoses.
The PCS code set, on the other hand, is one of two procedural coding systems. But unlike CPT®, ICD-10-PCS is used strictly in hospital inpatient healthcare settings.