ICD-9 diagnosis codes are largely obsolete, replaced by ICD-10 in most countries for better specificity and data accuracy. The U.S. mandated the switch to ICD-10-CM for most healthcare settings by October 1, 2015, under HIPAA regulations. However, some limited use of ICD-9 persists:
- Workers’ Compensation and Auto Insurance: Certain U.S. payers, like workers’ compensation programs and auto insurers, were not covered by HIPAA and continued using ICD-9 for billing and claims processing in some cases, though many have transitioned to ICD-10.
- Historical Data Analysis: Researchers and public health analysts may use ICD-9 codes when studying pre-2015 medical records or longitudinal datasets that span the transition period.
- Legacy Systems: Some smaller healthcare providers or systems with outdated software might still reference ICD-9 for internal records, though this is rare and decreasing due to regulatory pressures.
- Non-HIPAA Entities: Entities not subject to HIPAA, like some international organizations or niche insurance programs, might still use ICD-9, but this is uncommon.
Globally, the World Health Organization stopped supporting ICD-9 after ICD-10’s adoption in 1994, and many countries moved to ICD-10 years before the U.S. ICD-11, launched in 2022, is now being adopted in some regions, further phasing out older systems.