ICD-10 Overview
ICD-10 diagnosis codes differ from ICD-9 codes in the following ways:
| ICD-9-CM, Volumes 1 and 2 | ICD-10-CM |
| 14,315 codes (Fiscal year 2010) | 69,101 codes (2010 version) |
| Numeric or alphanumeric | Alphanumeric |
| Three to five characters long | Three to seven characters long |
For more information, see AHIMA’s
ICD-10 CM Primer.
ICD-10 procedure codes differ from ICD-9 procedure codes in the following ways:
| ICD-9-CM, Volume 3 | ICD-10-PCS |
| 3,838 codes (Fiscal year 2010) | 71,957 codes (2010 version) |
| Numeric | Alphanumeric |
| Three or four characters long | Seven characters long |
ICD-10 is organized differently from ICD-9. In some cases it is more detailed, so users might need to provide additional information during clinical documentation. These additional details are intended to increase accuracy in documentation and billing and to improve statistical analysis. Clinicians who are used to selecting diagnoses that do not include these details might need to begin providing more information.
The additional detail in ICD-10 makes any mapping from ICD-9 difficult. It is not possible to automatically convert codes from ICD-9 to ICD-10. To help with conversion, CMS publishes two main mappings:
- The General Equivalence Mappings (GEMs) translate from ICD-9 to ICD-10 and ICD-10 to ICD-9 with as much clinical equivalence as possible. This focus on clinical equivalence makes the mappings harder to use for billing. An ICD-9 code might be clinically equivalent to multiple ICD-10 codes, so billing users have to determine which ICD-10 code to use. This is the most clinically accurate mapping and a useful reference.
- CMS Reimbursement mappings provide an automated conversion from ICD-10 to ICD-9 for billing purposes. However, these mappings do not guarantee clinical equivalence. CMS designed these mappings to support payors that are unable to process ICD-10 codes immediately after the transition so they can receive claims in ICD-10 but adjudicate them in ICD-9.