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. The CDC’s National Center for Health Statistics is responsible for the clinical modification of ICD-10 for use in the United States, which is ICD-10-CM; CMS maintains the companion inpatient procedure system, ICD-10-PCS.
In practice
Diagnosis coding drives medical-necessity edits: a claim whose diagnosis does not support the billed service can be denied on that basis. Releases follow the federal fiscal year, which runs October 1 through September 30 — but they are not only annual. NCHS has issued mid-year releases effective April 1 that replace the October 1 set for the remainder of the year, so the codes that apply are the ones in effect on the date of service, not the ones from the most recent October.
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.