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The United States Core Data for Interoperability (USCDI) is a standardized set of health Data Classes and constituent Data Elements published by the Assistant Secretary for Technology Policy / Office of the National Coordinator for Health Information Technology (ASTP/ONC) to support nationwide electronic health information exchange. Incorporated by reference at 45 CFR § 170.213, USCDI defines what clinical and administrative data elements certified Electronic Health Record (EHR) systems must expose, while technical implementation specifications—specifically HL7 FHIR US Core and HL7 C-CDA—define how those elements are formatted and transmitted across FHIR APIs.
What Is USCDI? (Data Classes vs. Data Elements and Vocabulary Bindings)
Created under the 21st Century Cures Act Final Rule (85 FR 25642) to replace the older Common Clinical Data Set (CCDS), USCDI is organized as a two-tier taxonomy paired with mandatory federal vocabulary standards:
- Data Class: An aggregation of granular data elements by a common clinical or administrative theme—such as Allergies and Intolerances, Clinical Notes, Immunizations, Laboratory, Medications, Patient Demographics/Information, Problems, Procedures, and Vital Signs.
- Data Element: The most granular level at which a piece of health information is exchanged within a Data Class. For example, inside the Vital Signs Data Class, individual Data Elements include Systolic Blood Pressure, Diastolic Blood Pressure, Heart Rate, Respiratory Rate, Body Temperature, Body Weight, Body Height, and Pulse Oximetry.
- Standardized Terminology Bindings: Rather than permitting free-text or proprietary local hospital codes, USCDI maps Data Elements to federal vocabulary standards codified at 45 CFR § 170.207: SNOMED CT and ICD-10-CM for problems and procedures, LOINC for laboratory tests, clinical notes, and vital signs, RxNorm and NDC for medications, and CVX/NDC for immunizations.
Comparison of USCDI Versions: USCDI v1 vs. v2 vs. v3 vs. v4 vs. v5
ASTP/ONC updates USCDI on an annual cycle through the public ONC New Data Element and Class (ONDEC) submission system, advancing candidate elements from Level 0 through Level 1 and Level 2 before inclusion in a published draft and final version. Developers can adopt newer versions ahead of federal rulemaking under the Standards Version Advancement Process (SVAP):
| USCDI Version | Regulatory Status under 45 CFR § 170.213 | Corresponding HL7 FHIR US Core IG | Major Added Data Classes & Elements |
|---|---|---|---|
| USCDI v1 (July 2020) | Initial Cures Act Final Rule baseline (expired as standalone baseline January 1, 2026) | US Core STU 3.1.1 | 16 foundational Data Classes (~50 Data Elements), including Clinical Notes (8 note types), Provenance (Author Time Stamp, Author Organization), Pediatric Vital Signs, and Address/Phone/Email. |
| USCDI v2 (July 2021) | SVAP voluntary advancement version | US Core STU 4.0.0 | Added Clinical Tests and Diagnostic Imaging Data Classes; introduced Sexual Orientation, Gender Identity (SOGI), and 4 Social Determinants of Health (SDOH) elements (Assessment, Goals, Interventions, Problems/Health Concerns). |
| USCDI v3 (July 2022) | Mandatory ONC HTI-1 Final Rule baseline (required for all certified EHRs as of January 1, 2026) | US Core STU 6.1.0 | Added Health Insurance Information and Health Status/Assessments Data Classes; added Specimen type, Result status, Disability Status, Mental/Cognitive Function, Pregnancy Status, Tribal Affiliation, and Date of Death. |
| USCDI v4 (July 2023) | SVAP-approved version (incorporated in HTI-2 / voluntary adoption) | US Core STU 7.0.0 | Added Facility Information Data Class; added Vital Signs averages, Encounter Identifier, Medication Adherence, Treatment Intervention Preference, and Care Experience Preference. |
| USCDI v5 (July 2024) | SVAP-approved version | US Core STU 8.0.0 | Added Observations and Orders Data Classes; added Advance Directive Observation, Emergency Department Note, Operative Note, Lot Number (Medications), and Pronouns/Name to Use. |
How Do 45 CFR § 170.213, the ONC HTI-1 Rule, and Information Blocking Govern USCDI?
USCDI sits at the center of three federal regulatory mandates affecting hospitals, ambulatory practices, payers, and clinical software vendors:
- ONC Health IT Certification Program (45 CFR § 170.213 & § 170.315): Under the ONC HTI-1 Final Rule (89 FR 1192), certified health IT modules listed on the Certified Health IT Product List (CHPL) were required to transition from USCDI v1 to USCDI v3 by January 1, 2026. This applies to the Standardized API for Patient and Population Services (
45 CFR § 170.315(g)(10)using SMART on FHIR), Transitions of Care (§ 170.315(b)(1)), View, Download, and Transmit (§ 170.315(e)(1)), and Electronic Case Reporting (§ 170.315(f)(5)). - CMS Interoperability and Prior Authorization Mandate (CMS-0057-F): Medicare Advantage organizations, state Medicaid/CHIP agencies, and Qualified Health Plan (QHP) issuers on the Federally-facilitated Exchanges must expose USCDI clinical data classes via Patient Access, Provider Access, and Payer-to-Payer FHIR APIs.
- 21st Century Cures Act Information Blocking Rules (45 CFR Part 171): While the statutory definition of Electronic Health Information (EHI) under 45 CFR § 171.102 expanded on October 6, 2022 to encompass the entire HIPAA Designated Record Set (not merely USCDI v1), USCDI remains the core baseline of structured data guaranteed to be accessible without special effort via certified EHR APIs.
How Is USCDI Used in Clinical Research, eSource, and USCDI+ Domain Extensions?
For clinical trial sponsors, biomedical registries, and health services researchers, USCDI reduces the need for manual chart abstraction when pulling real-world data (RWD) from hospital EHRs:
- Direct EHR-to-EDC eSource Extraction: Using the HL7 Vulcan FHIR-to-CDISC mapping guides, clinical trial platforms query USCDI-mandated FHIR resources (
Patient,Condition,MedicationRequest,Observation,DiagnosticReport, andDocumentReferencefor USCDI Clinical Notes) to pre-populate Electronic Data Capture (EDC) case report forms. - USCDI+ Domain-Specific Extensions: Recognizing that specialized research and public health domains require granular elements beyond the universal EHR baseline, ASTP/ONC launched USCDI+ in partnership with federal agencies—including USCDI+ Cancer (with NCI and FDA for oncology clinical trials and registries), USCDI+ Public Health (with CDC), USCDI+ Quality (with CMS for electronic clinical quality measures [eCQMs]), and USCDI+ Maternal Health.
