USCDI
United States Core Data for Interoperability
USCDI is the ONC-maintained, versioned list of data classes and elements that must be available for nationwide health information exchange.
USCDI (United States Core Data for Interoperability) is a standardized set of health data classes and constituent data elements — such as patient demographics, problems, medications, lab results, clinical notes, and, in newer versions, social determinants of health — that ONC requires be exchangeable.
USCDI is versioned (v1, v2, v3, v4, and onward). ONC ratchets the required content over time through rules like HTI-1 and HTI-2, steadily expanding what must flow in standard formats. US Core FHIR profiles are the vehicle that carries USCDI data.
For implementers, USCDI answers the question "what data, at minimum, must move?" while US Core and FHIR answer "in exactly what structure?" CMS-0057-F references USCDI as the data-content baseline for its FHIR APIs.
How this relates to Health1st
Health1st's Terminology Agent normalizes local codes and value sets to the USCDI-aligned bindings US Core expects, so the data classes a payer or provider is obligated to exchange come out coded correctly rather than as free text.
Related terms
US Core is the HL7 implementation guide that constrains FHIR resources into the specific profiles US regulation requires, binding them to USCDI data elements.
FHIR is HL7's modern, web-native standard for exchanging healthcare data as modular JSON/XML resources over RESTful APIs.
CMS-0057-F requires impacted US payers to stand up four FHIR APIs — Patient Access, Provider Access, Payer-to-Payer, and Prior Authorization (PARDD) — with API compliance generally due January 1, 2027.
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