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ICD 10 Frequently Asked Questions

What is ICD-10-CM and why is it important?

ICD-10-CM is the International Classification of Diseases, 10th Revision, and Clinical Modification. It is a new diagnosis classification system developed by the Centers for Disease Control and Prevention (CDC) for use in all United States healthcare settings. ICD-10-CM will replace the existing diagnosis code set, ICD-9-CM (International Classification of Diseases, 9th Edition, Clinical Modification, Volumes 1 and 2). The U.S. Department of Health and Human Services (HHS) has mandated that all HIPAA-covered entities must implement ICD-10-CM for use in standard electronic transactions (including but not limited to claims) for dates of service that occur on or after the  compliance date. 

What is ICD-10- PCS and why is it important?

ICD-10-PCS is the Procedure Classification System developed by CMS for use in the United States for hospital inpatient settings only. It will replace ICD-9-CM Volume 3 as the code set for reporting hospital inpatient procedures in HIPAA standard electronic transactions for dates of service on or after the compliance date.

What is the ICD-10 compliance date?

Please visit the CMS ICD10 web page for the latest news about ICD-10 and the compliance date.

How does ICD-10 coding differ from ICD-9 coding?

ICD-10 is not just an update of ICD-9 codes. It is a restructuring of the diagnosis classification system with far more alpha numeric codes, expanded code lengths and narrative descriptions allowing for greater granularity. The following table illustrates the key differences:


Classification System

Number of Codes




·         3-5 digits

·         Digit 1 is alpha (E or V) or numeric

·         Digits 2-5 are numeric



·         3-7 digits

·         Digit 1 is alpha

·         Digit 2 is numeric

·         Digits 3-7 are alpha or numeric

ICD-9 Volume 3

4,000 Approximate number in use today

·         3-4 digits, decimal after second digit

·         Numeric

·         Not multiaxial


200,000 (Approximate number)

·         7 digits, no decimal

·         Alphanumeric


Why does the insurance industry have to implement ICD-10?

On January 16, 2009, the U.S. Department of Health and Human Services (HHS) released the final rule mandating that everyone covered by the Health Insurance Portability and Accountability Act (HIPAA) must implement ICD-10 for medical coding..  Please visit the  CMS ICD10 web page for the compliance date and the latest news about ICD-10.

Are there crosswalks available to map ICD-9-CM codes to ICD-10-CM codes?

Centers for Medicare and Medicaid Services (CMS) and the Centers of Disease Control and Prevention (CDC) have developed General Equivalence Mappings (GEMs) to show generally equivalent relationships between ICD-9-CM codes and ICD-10-CM codes. CMS has also created reimbursement mappings to refine the mappings developed in GEMs. However, the greater granularity of ICD-10-CM compared to ICD-9-CM often result in one-to-many, one-to-none, and many-to-many mappings in addition to one-to-one mappings.

The Coordination & Maintenance Committee advises CMS on changes to the crosswalk between the Ninth and Tenth Revisions of the International Classification of Diseases (ICD-9 and ICD-10, respectively)  The Patient Protection and Affordable Care Act of 2010 (PPACA) requires that any revised crosswalk be treated as a code set for which a standard has been adopted by the U.S. Department of Health and Human Services (HHS) Secretary and that revisions to this crosswalk be posted to the CMS  website .  

What steps should covered entities take to prepare for ICD-10?

Implementation planning for ICD-10- should begin immediately if not already underway, regardless of the size or function of the covered entity. ICD-10  implementation is not just a billing project or an IT project. For most covered entities, the organizational impact of the transition will be broad and deep.

An impact assessment should be completed as soon as possible to enable timely planning, development, education, testing, and implementation. Several organizations provide implementation planning resources for ICD-10. View a timeline on the CMS ICD-10 webpage.