Part 1: The Differences Between ICD-9 and ICD-10 - Source AMA [American Medical Association]

Alert: The new ICD-10 compliance date is October 1, 2015.

The ICD-10 code sets are not a simple update of the ICD-9 code set. The ICD-10 code sets have fundamental changes in structure and concepts that make them very different from ICD-9. Because of these differences, it is important to develop a preliminary understanding of the changes from ICD-9 to ICD-10. 

Issues today with the ICD-9 diagnosis and procedure code sets are addressed in ICD-10. One concern today with ICD-9 is the lack of specificity of the information conveyed in the codes. For example, if a patient is seen for treatment of a burn on the right arm, the ICD-9 diagnosis code does not distinguish that the burn is on the right arm. If the patient is seen a few weeks later for another burn on the left arm, the same ICD-9 diagnosis code would be reported. Additional documentation would likely be required for a claim for the treatment to explain that the burn treated at this time is a different burn from the one that was treated previously. In the ICD-10 diagnosis code set, characters in the code identify right versus left, initial encounter versus subsequent encounter, and other clinical information.

Another issue with ICD-9 is that some chapters are full and impede the ability to add new codes. In some cases, new codes have been assigned to different chapters making it difficult to locate all available codes. ICD-10 codes have increased character length, which greatly expands the number of codes that are available for use. With more available codes, it is less likely that chapters will run out of codes in the future.

Other issues that are addressed in ICD-10 include the use of full code titles and appropriately reflecting advances in medical knowledge and technology. More detailed information and examples are provided below to demonstrate the differences between the ICD-9 and ICD-10 code sets.