The United States Core Data for Interoperability (USCDI) is a standardized set of health data classes and data elements, published and versioned by the ONC, that health IT must be able to exchange for nationwide interoperability. It defines what data (allergies, medications, problems, lab results, clinical notes, provenance, and more) must move; the US Core FHIR implementation guide defines how. USCDI expands on a predictable schedule, ratcheting the interoperability floor upward.
USCDI
USCDI is the answer to ‘which data has to be shareable’ in US healthcare. It is a versioned list of data classes and elements — allergies, medications, problems, labs, clinical notes, provenance — that ONC requires certified health IT to exchange, and it is deliberately designed to grow.
- The what, not the how - USCDI names the data; FHIR and US Core carry it. The two are meant to be read together.
- Versioned and expanding - Each release adds elements, so the interoperability floor ratchets up on a published cadence rather than freezing.
- The dataset the mandate is built on - The Cures Act information-blocking rule and ONC certification both revolve around exposing USCDI through a standardized API.
For my purposes USCDI is the clearest example of the healthcare-mandate pattern: a genuinely good, government-and-industry-agreed data standard that produced existence — every certified EHR can emit USCDI over FHIR — without producing usability. The data floor is real; the examples, consent surface, and governance that would turn it into a product are the parts the rule did not reach, and the parts my scoring keeps finding empty.
Referenced in API Evangelist papers
This standard shows up in my published research. These reports read the machine-readable evidence provider by provider — and put this standard in the context of a real sector.
The State of US Healthcare APIs
USCDI is the data floor the Cures Act made every certified EHR expose — as a compliance obligation, not a product.
Governed by these regulations
A standard is the machine-readable contract; a regulation is the law that requires it. These are the regulations that mandate or drive this standard, catalogued at regulations.apievangelist.com.
ONC Health IT Certification Program
ONC publishes USCDI and requires certified health IT to support the current version.
21st Century Cures Act
USCDI is the standardized dataset the information-blocking rule is built around.
