ICD-10
ICD-10 is the diagnosis coding system used in the US to report a patient’s condition on a claim — the “why” that justifies a service.
Updated
ICD-10 — the International Classification of Diseases, 10th Revision — is the code system used to report diagnoses. In the US, ICD-10-CM (Clinical Modification) codes report the patient’s condition on claims in every care setting, and ICD-10-PCS codes report inpatient hospital procedures.
A claim pairs the diagnosis (ICD-10-CM) with the service (CPT/HCPCS) to establish medical necessity — the diagnosis explains why the service was appropriate. ICD-10-CM is maintained by CMS and the CDC’s National Center for Health Statistics.
In practice
Diagnosis coding drives medical-necessity edits: a diagnosis that does not support the billed service is a common denial reason. ICD-10-CM is updated annually, effective October 1.
Commonly confused with
- CPT code: ICD-10-CM says why a service was needed; CPT says what was done.
- ICD-10-PCS: ICD-10-PCS codes inpatient hospital procedures; ICD-10-CM codes diagnoses across all settings.