The ARRA included the Health Information Technology for Economic and Clinical Health (HITECH) Act, which as part of the EHR incentive programs -now called Promoting Interoperability, required use of certified electronic health record (EHR) technology. The Office of the National Coordinator for Health Information Technology (ONC) established the initial set of standards, implementation specifications, and certification criteria for EHRs codified at 45 C.F.R. § 170. Subpart C is specific to the certification criteria.

MACRA (P.L. 114-10) continued with a mandate for widespread interoperability among these systems with requirements for CMS to develop metrics for successful interoperability. MACRA defined interoperability in § 106(b)(1)(B)(ii) as

• the ability of two or more health information systems or components to exchange clinical and other information and to use the information that has been exchanged using common standards as to provide access to longitudinal information for health care providers in order to facilitate coordinated care and improved patient outcomes.

An aim of the 21st Century Cures Act (Public Law [P.L.] 114-255) (Cures Act) is to increase data-sharing and interoperability via the expanded use of health information technology (IT) and the creation of partnerships between health information exchange organizations and measured entities. The increase in data-sharing is also meant to increase person access to EHRs and thus improve patient care. The Cures Act defined in § 4003(a)(2) interoperability, with respect to health IT, as health IT that—

‘‘(A) enables the secure exchange of electronic health information with, and use of electronic health information from, other health information technology without special effort on the part of the user;

‘‘(B) allows for complete access, exchange, and use of all electronically accessible health information for authorized use under applicable State or Federal law; and

‘‘(C) does not constitute information blocking as defined in section 3022(a).’’

ONC defines USCDI as “a standardized set of health data classes and constituent data elements for nationwide, interoperable health information exchange.” A data class is “an aggregation of various data elements by a common theme or use case” and a data element is “the most granular level at which a piece of data is represented in the USCDI for exchange.” USCDI v1 contains 16 data classes, e.g., patient demographics and procedures. Each data element is associated with a specific version of one or more standard vocabulary. Version 1 is the base requirement and the ONC 21^st Cures Act final rule allows health IT developers to adopt and implement newer versions of the USCDI.

ONC has a data element and class submission system for people to suggest/submit ideas for new data elements and/or data classes. After a public comment period, ONC published version 2 in July 2021 and published version 3 with errata in October 2022. Version 3 has 19 data classes.

USCDI v1 patient demographics includes race, ethnicity, birth sex, and preferred language all with applicable terminology standards. The health IT certification criteria published in 2015 requires certified health IT to be capable of recording standardized data on a patient’s sexual orientation and gender identity, but USCDI v1 does not include these data elements and there are no terminology standards associated with the requirement. USCDI v2 added sexual orientation and gender identity to the patient demographics data class and changed birth sex to sex assigned at birth. Also, with a focus on health equity, v2 added the SDOH data class, courtesy of The Gravity Project, and four SDOH data elements to enable identification of specific needs in domains such as food, housing, and transportation insecurity, and to coordinate care and assistance to improve health outcomes.

USCDI+ is a new ONC initiative supporting the identification and establishment of domain or program-specific datasets operating as extensions to the existing USCDI. USCDI+ is a service ONC is providing to federal partners, starting with CMS and the Centers for Disease Control and Prevention for quality measurement and public health. The USCDI+ has three pillars – collaboration, harmonization, and specification. The processes for USCDI+ are the same as the USCDI with some additions:

• A discovery process and charter
• Identification of use cases, data specifications, and agency programmatic incentives/requirements for use of any specific USCDI+ dataset
• Evaluation of data classes/elements according to objective criteria, such as industry priority and readiness, level of standards maturity, and identified agency need 

The ISA is a process used by ONC to provide interoperability standards and implementation specifications for health IT. The ISA is dynamic, meaning updates can occur at any time, and has four sections:

• Vocabulary/Code Sets/Terminology Standards and Implementation Specifications (i.e., “semantics”)
• Content/Structure Standards and Implementation Specifications (i.e., “syntax”)
• Standards and Implementation Specifications for Services and Exchange (i.e., the infrastructure components deployed and used to address specific interoperability needs)
• Administrative Standards and Implementation Specifications (i.e., payment, operations and other "non-clinical" interoperability needs)

The ISA provides information such as whether the Federal Government requires the item. Certification of health IT requires use of USCDI v1.