Understanding the US Core Implementation Guide and USCDI

Explore US healthcare IT with a focus on the US Core Implementation Guide and USCDI, vital for enhancing interoperability and patient care. Regulatory bodies like ONC and CMS introduced these tools under the Cures Act to standardize healthcare data exchange. This article explains what US Core is, how it differs from USCDI, and the latest updates to the US Core Implementation Guide.

Globally, there has been a significant push for digitalization and interoperability within healthcare. The US stands at the forefront of these changes with regulatory frameworks and standards. Agencies like the Office of the National Coordinator for Health Information Technology (ONC) and the Centers for Medicare & Medicaid Services (CMS) play a pivotal role in implementing and enforcing regulations that significantly impact the development and use of healthcare IT systems. 

They developed the United States Core Data for Interoperability (USCDI) and the FHIR-based US Core Implementation Guide. These tools are critical in standardizing data formats and ensuring seamless data exchange across various healthcare platforms and systems, thereby enhancing the quality and continuity of patient care.

ONC Certification

The Cures Act final rule, particularly § 170.315(g)(10) and § 170.315(b)(10), establishes critical criteria for standardized APIs for patient and population services and the export of electronic health information. Within this framework, the United States Core Data for Interoperability (USCDI) and the US Core FHIR Implementation Guide (IG) emerge as key components. USCDI was developed under the guidance of the ONC to standardize data classes and elements essential for healthcare data exchange.

What Is USCDI?

USCDI, or the United States Core Data for Interoperability, is a standardized set of healthcare data elements. Its purpose is to ensure a consistent and seamless exchange of electronic health information across different systems. It provides a technical foundation that underpins data-sharing initiatives, enhancing interoperability in healthcare. There are multiple versions of USCDI, each building upon its predecessor to include a broader range of data elements and classes, reflecting the evolving needs of the healthcare sector.

The US Core Implementation Guide and US Core Profiles

The US Core Implementation Guide is a vital tool for developers and healthcare organizations. It offers detailed guidelines on how to implement FHIR in a manner that aligns with USCDI standards. This guide includes a set of US Core Profiles, which are specific requirements for different types of healthcare data, such as patient demographics, clinical notes, and laboratory results. These profiles play a crucial role in ensuring FHIR-based systems are compliant with USCDI, fostering a more interoperable healthcare ecosystem.

US Core Patient FHIR Profile Example

US Core Patient Profile Differential Table Example 

Recent updates from the January 2024 ballot, reflecting the new US Core Data for Interoperability (USCDI) v4 Data Elements and Classes, have further refined these profiles. For instance, the US Core Allergy Intolerance Profile now includes non-pharmacologic agents, while the US Core Location Profile was updated to support Facility Identifier and Type, enhancing data detail and interoperability capabilities.

Moreover, new profiles like the US Core Average Blood Pressure Profile and updates to the US Core Medication Request Profile, which now supports Medication Adherence, demonstrate the evolving nature of these standards. These updates ensure that US Core Profiles remain aligned with the latest healthcare data requirements, such as those for treatment preferences and health status assessments.

The US Core Profiles have become the foundation for US Realm FHIR implementation guides, reflecting the changes in USCDI and the feedback from the US Realm FHIR community. These profiles set the minimum constraints on FHIR resources and define the interactions necessary for accessing patient data. This dual approach, Profile Only Support and Profile Support + Interaction Support, offers flexibility in implementation, catering to various needs within the healthcare IT ecosystem.


The US Core Implementation Guide provides the technical framework for implementing FHIR in the US; the USCDI defines the specific data elements and classes that need to be shared across different health information systems to achieve interoperability. The implementation guide is about the “how” of FHIR implementation, while the USCDI is about “what” data needs to be interoperable.

US Core Implementation Requirements

The US Core requirements define within the profiles the minimum necessary elements, extensions, vocabularies, and Value Sets, and they constrain how elements are used within the profile’s framework. 

For US Core Profile elements, there are three categories: Mandatory, Must Support, and Additional USCDI Requirements. Mandatory elements are compulsory with a minimum cardinality of one. Must Support elements set the expectations for the server and client, defined by US Core. Additional USCDI Requirements are essential for ONC Health IT Certification and for certified systems, and they are treated as equivalent to Must Support elements. 

Want to learn more about the ONC Certification Program? 

Check out our in-depth guide on how to pass the ONC certification, which is part of the US FHIR compliance, including Inferno Framework testing for § 170.315(g)(10) (Standardized API for patient and population services) and § 170.315(b)(10) (Electronic Health Information export).  

What you will learn from this whitepaper:

  • Understand the mandatory nature and implications of ONC certification for your health IT product’s success.
  • Navigate the complex requirements and align your solution with the rigorous standards of functionality, security, and interoperability.
  • Gain comprehensive insights into the § 170.315(g)(10) Standardized API for Patient and Population Services criterion.
  • Learn practical insights and actionable steps to prepare your product for the Inferno Testing Framework Process and streamline the certification experience.

Post author

Stanislav Ostrovskiy

Partner, Business Development at Edenlab

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