What is ICD? What’s the difference between ICD-9 and ICD-10?

what is icd

ICD is the International Classification of Diseases created by the World Health Organization more than 100 years ago. ICD codes are used to report medical diagnoses and inpatient procedures. The United States has been using the ICD-9 version since 1979, and is currently in the process of transitioning to ICD-10. By October 1st, 2015 everyone covered by the Health Insurance Portability Accountability Act (HIPAA) – and not just those who submit Medicare or Medicaid claims – must implement the new code sets but, what does that entail? What will change?

Differences between ICD-9 and ICD-10 diagnosis codes



No laterality.

Laterality; right or left account for >40% of codes

3 to 5 digits.

1st digit is alpha (E or V) or numeric.

Digits 2 to 5 are numeric.

Decimal placed after 3rd character.


Seven digits

1st digit is alpha; 2nd digit is numeric.

Digits 3 to 7 are alpha or numeric.

Decimal placed after 3rd character.


No placeholder characters.

‘X’ placeholders.

14,000 codes

69,000 codes for better specificity.

Limited severity parameters.

Extensive severity parameters.

Limited combination codes.

Extensive combination codes for better complexity.

One type of excluded notes.

Two types of excluded notes


Example: Femur fracture



·         Before compliance date:

·         821.11

·         Open fracture of shaft of femur.

·         All codes for femur fracture: 16

·         After compliance date:

·         S72.351C

·         Displaced comminuted fracture of shaft of right femur, initial encounter for open fracture type IIIA, IIIB, or IIIC.

·         All codes for femur fracture: 1530


Other major changes in ICD-10 include:

·         Injuries are grouped by anatomical site as opposed to injury type.

·         The ICD-9 codes corresponding to V (Factors Influencing Health Status and Contact with Health Services) and E (External Causes of Injury and Poisoning) codes are implemented into the main classification instead of separated into supplementary classifications as in ICD-9.

·         New code definitions are supplied to reflect modern medical practice. For instance, definition of acute myocardial infarction is four weeks and not eight weeks.

·         Certain conditions and disorders are classified differently as a result of category restructuring and code reorganization in a several ICD-10-CM chapters.

·         Certain conditions are reclassified to different chapters or sections, reflecting current medical knowledge.

 When it comes to ICD-10, it is important to also establish the difference between fact and fiction. Like any new policy, the new coding protocol has been subject to myth-making, some of which myths are debunked below:



The Department of Health and Human Services (HHS) will grant an extension beyond the October 1, 2015, compliance date.

HHS has no plans to extend the compliance date for implementation of ICD-10; all covered entities must take steps to implement the new code sets by Oct. 1st 2015.

ICD-10 was developed without clinical input.

A number of medical specialty societies contributed to the development of the coding systems.

No hard copy ICD-10 code books will be available. All coding will need to be performed electronically.

Code books are already available and are a manageable size. ICD-10 is not predicated on electronic hardware and software.

ICD-10 is already outdated.

ICD-10-CM codes have been updated annually since their original development to keep up with advances in medicine and technology and changes in the healthcare environment.

State Medicaid Programs will not be required to update to ICD-10 codes.

The Centers for Medicare and Medicaid Services will work with State Medicaid Programs to ensure ICD-10 is implemented on time.

Medically unnecessary diagnostic tests will be performed to assign an ICD-10 code.

As with ICD-9, ICD-10 codes are derived from documentation in the medical record. If a diagnosis has not yet been established, the condition is coded to its highest degree of certainty when using both coding systems. In fact, ICD-10 has many more codes for signs and symptoms than ICD-9, and it is better designed for use in ambulatory encounters when definitive diagnoses are often not yet known. Nonspecific codes are still available in ICD-10 for use when more detailed clinical information is unknown.

ICD-10 will replace Current Procedural Terminology (CPT)

ICD-10 will only be used for facility reporting of hospital inpatient procedures and will not affect CPT.