ICD-9-CM is the U.S. clinical modification of ICD-9 that provided expanded diagnosis detail for clinical and administrative use.
In clinical research, ICD-9-CM appears in legacy EHR and claims datasets used for feasibility, epidemiology, and retrospective analyses. Correct use supports standardized reporting of comorbidities, outcomes, and medical history for older data sources. Sponsors often require clear versioning and mapping approaches to maintain analytic validity. Appropriate governance reduces coding inconsistencies that can affect endpoint interpretation.