US Core
US Core Implementation Guide
US Core is the HL7 implementation guide that constrains FHIR resources into the specific profiles US regulation requires, binding them to USCDI data elements.
US Core is the FHIR implementation guide that defines how core clinical data must look in the United States. It constrains base FHIR resources into named profiles (US Core Patient, US Core Condition, US Core Observation, and so on) and binds their elements to required terminologies and value sets.
US Core is the conformance target that ties FHIR to policy: it operationalizes the USCDI data classes and is referenced directly by ONC certification and by CMS interoperability rules. CMS-0057-F, for example, names US Core STU 3.1.1 as part of its mandated technical stack.
Passing US Core validation is often the practical gate for integration: trading partners and auditors want conformance reports proving that generated FHIR meets the profile, not just that it is well-formed JSON.
How this relates to Health1st
Health1st's Conformance & Validation Agent checks every generated FHIR resource against US Core (and other IGs), explains any validation failure in plain language, and produces conformance reports you can hand to a security or procurement reviewer.
Related terms
FHIR is HL7's modern, web-native standard for exchanging healthcare data as modular JSON/XML resources over RESTful APIs.
USCDI is the ONC-maintained, versioned list of data classes and elements that must be available for nationwide health information exchange.
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.
Da Vinci is the HL7 accelerator that publishes FHIR implementation guides for payer–provider workflows, including prior authorization, coverage, and data exchange.
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