Interoperable Digital Identity and Patient Matching
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Interoperable Digital Identity and Patient Matching, published by HL7 International - Patient Administration WG. This guide is not an authorized publication; it is the continuous build for version 2.0.0-draft built by the FHIR (HL7® FHIR® Standard) CI Build. This version is based on the current content of and changes regularly. See the Directory of published versions

Digital Identity


Digital Identity is the unique representation of a subject engaged in an online transaction. Digital identities involved in healthcare transactions can correspond to Patients, Providers, Payers, and other healthcare actors. The combination of a legal, distinct, verified organization name and the state in which it is verified uniquely establishes Organizational Identity as defined in this guidance. A digital identity SHALL always be unique in the context of a digital service compliant with this IG, but does not necessarily need to uniquely identify the subject in all contexts. Specifically, such a digital service SHALL NOT require that a human subject’s real-life identity is evident from the credential identifier on its own.

In an effort to address matching errors by prioritizing the use of Digital Identifiers, this section of the IG defines what are likely to be new Digital Identifiers suitable for use in person matching where high confidence in the Digital Identity associated with such an Identifier is needed. Though there are benefits in having just one such credential, an individual’s choice to use multiple such Digital Identifiers each from a different service, also referred to an Identity provider or Assigner, is also consistent with the IG’s requirements. This section of the IG also describes Enterprise Identifiers which are the next best option when a Digital Identifier is unavailable or has not yet been established. In this context, “Enterprise Identifiers” are identifiers issued by assigners who have not implemented the stricter requirements necessary for Digital Identifiers. For example, a clinic that leverages insurance member IDs for identifiers and therefore requires additional demographics to be provided during a match request to the insurance company because the identifier is not 1:1 with a unique identity.


Requirements for Digital Identifiers for Individuals

  • Identifier SHALL be capable of a validation process. Acceptable validation methods include 1) the user authenticates themselves at a level of authentication assurance commensurate with that of the credential itself and the credential is confirmed to originate from a trusted Identity Provider – authentication assurance SHALL be AAL2 or greater for any identity assurance level greater than IAL1; 2) relying party queries the Identity Provider’s system to confirm demographics associated with the individual in a privacy preserving way, for example by presenting a cryptographic hash of first, last, date of birth (DOB) and home street address including zip code or city and state along with the Identifier; or 3) authenticated individual authorizes sharing of demographics with the relying party. Acceptable verification methods include: 1) Identifier matches an Identifier previously associated to the medical record; 2) the Individual Profile Photo associated with an OpenID Connect Credential bound to the Identifier is consistent with this IG and NIST 800-63A requirements on the use of biometrics and is a visual match to the individual or to a government-issued photo ID previously associated with the individual during a documented Identity Proofing event and saved in their record.

  • A documented Identity Proofing process, performed by the Identity Provider directly and not through a Trusted Agent, at a minimum SHALL establish that a unique individual is represented by each Identifier and includes a declaration of identity assertion by the individual (such that it is fraudulent to claim a false identity). This requires the Identity Provider to follow a process that is IAL1.5 or higher according to this guidance. As future guidance may require an indication of individual attribute verification status, for example, a flag indicating whether an address was verified, and the verification date, Identity Providers SHOULD capture sufficient detail in their Identity Proofing records that their systems can differentiate between verified and unverified identity attributes.

  • Identifier SHALL be a version 4 (random) Globally Unique IDentifier (GUID or UUID as per RFC 4122) that remains unique to the person for all time within the assigner’s system: the UUID SHALL NOT be assigned to a different person later, and a different UUID SHALL NOT be assigned to that same person by the assigner.

  • Each Digital Identifier SHALL correspond 1:1 with a unique person on the Identity Provider’s (assigner’s) system: more than one Identifier SHALL NOT be generated within the assigner’s system for the same individual, as that would lead to mismatches on individual identity and potential patient safety issues. In-person processes and remote equivalents exist for binding a strong credential to a Person record. As one example, a digital credential from a third-party Identity Provider can be associated with a record when IAL2-verified Full Name, Home Address, and Date of Birth exist in both places and can be matched within the record and a Declaration of Identity was made to both the Identity Provider and the managing organization responsible for the Person record. In the case of a professional credential associated with an organization, the individual also asserted their legal authority to act as a representative of that organization and the existence and the Identity Provider verified the uniqueness of the organization at the same or a greater level of identity assurance. At a minimum, the organization name and state of existence are recorded and may be included with other verified demographics about the individual.

  • Identifier SHALL NOT ever be reassigned to a different individual except in the case of name changes.

  • The associated individual onboarding process SHALL require the individual to assert that any attributes they provide correspond to their own identity. Legal names SHALL be used and the use of work addresses or phone numbers or other attributes not belonging to the individual SHOULD be discouraged.

  • The email address and mobile number provided SHALL be under the individual’s exclusive control if used to secure the Identifier or an associated credential.

  • Identifier SHOULD be “FHIR-ready”: The Identifier can be associated with an OpenID Connect credential with OAuth 2.0 authentication capabilities initiated through HL7 SMART App Launch IG on its own, or with UDAP Consumer-Facing or UDAP Tiered OAuth for User Authentication with UDAP JWT-Based Authentication, asserted in a UDAP Business-to-Business) transaction within an Authorization Extension Object, or shared in another trusted context. Assigners which manage patient health records SHALL associate a patient with their Identifier using Patient.identifier where Identifier.system = "", corresponding to the Identity-HL7-Identifier naming system, to establish these identifiers within their own systems. The match responder SHALL return the appropriate matching patient when a query from a trusted party includes an Identifier as a search parameter or in a match request. When it exists, the Identifier SHOULD appear in OpenID Connect identity claims made to trusted healthcare relying parties; note, however, that the Identifier defined in this IG is distinct from the OpenID Connect subject identifier, as the following example demonstrates (Details about the identifier may be updated as it becomes more broadly adopted or is officially registered):

   "name": "Jane Doe", 
   "given_name": "Jane", 
   "family_name": "Doe", 
   "birthdate": "1979-01-01", 
   "address": { 
     "street_address": "1234 Hollywood Blvd.", 
     "locality": "Los Angeles", 
     "region": "CA", 
     "postal_code": "90210", 
     "country": "US"}, 
   "phone_number": "+1 (555) 777-1234", 
   "email": "", 

Alternatively, the HL7 Identifier may be included as a FHIR Identifier in the Resource referenced by the SMART fhirUser claim using the Identity-HL7-Identifier.

  • The combination of Identifier plus Assigner (if any) SHALL NOT be reassigned for an individual; therefore, the Identifier SHALL be protected like a Social Security Number and SHALL NOT be shared other than for patient matching purposes in a healthcare setting. The Identifier itself SHALL NOT be used as an OpenID Connect identifier and SHALL NOT be programmatically derived or otherwise possible to deduce from the OpenID Connect identifier since the OpenID Connect identifier may need to be re-issued from time to time, and individuals may want to use their OpenID Connect credential to authenticate themselves in other settings in which they do not wish to share personally identifiable information (PII). Identity Providers SHALL NOT enable an individual to authorize sharing of the Identifier with an endpoint that is not a trusted healthcare organization. For Identifiers assigned at any identity assurance level greater than IAL1, Identity Providers which establish a mechanism for proof of control of the credential SHALL associate with the Identifier an authenticator meeting NIST AAL2 or higher authentication assurance and that can be reset, in lieu of or supplemental to the OpenID Connect 1.0 workflow.

  • The Identifier and any associated credentials SHALL be managed in alignment with NIST 800-63A Digital Identity Guidelines except as specified otherwise in this IG.


Digital Identifier Workflow Example

Patient completes an IAL 1.8 or greater identity verification process with a healthcare organization at registration and/or check-in, and the resultant Digital Identifier is then associated with the patient’s record in that organization’s electronic health record (EHR). The process includes collection and verification of (at a minimum, verification of control) a personal mobile number and email address belonging to the patient. The Identity Provider binds the Digital Identifier to an OpenID Connect credential with AAL2 authentication assurance. The patient subsequently authenticates to their insurance company’s system using this credential, after which the insurance company uses the Digital Identifier in a match request to the healthcare organization. Because this strong identity assurance credential has been used to authenticate the individual to both systems, and the patient authorizes sharing of PII from the Identity Provider to the healthcare organization for identity resolution, the healthcare organization can confidently share the correct patient data with the requesting party. If needed, the health system can contact the account holder out of band for additional information or can request real-time identity verification.


Requirements for Enterprise Identifiers

Locally-established business identifiers used in cross-organizational matching, including temporary identifiers, SHALL correspond to unique identities in the real world. In other words, business identifiers used in cross-organizational matching SHALL be chosen such that the identifer was not previously used for a different individual and SHALL NOT be reassigned to a different person in the future. NOTE that these are examples of what can be used for matching and may not meet all the requirements required of a Digital Identifier as defined in this IG.


  • Unique for the individual person (i.e., not the same identifier for entire family) within organizational boundaries of the exchange partner
  • “assigner” plus “identifier”/ (number) is not reusable for a different person
  • Can be stored as an identifier along with its assigner in FHIR Patient resource and therefore used in $match operations or other transactions
  • Identifiers with date issued, expiration date, or other validity period will contain this metadata when available.
  • Assigners SHOULD avoid the letters I and O in identifiers, as they are difficult to differentiate from numbers 1 and 0.


Enterprise Identifier Workflow Example

Patient provides their identifier(s) to a healthcare organization at registration and/or check-in, and the identifier(s) is/are then associated with the patient’s record. As an alternative to such an in-person binding to the record, patient rosters could be shared that describe how to associate each patient medical record number and insurance identifier pairing, for example, to manage identities at scale.


Miscellaneous Established Identifiers

Absent a Digital Identifier or Enterprise Identifier as described above, other identifiers are helpful in best practice person matching, for example:

  • Social Security Numbers/Last 4
  • Driver’s License Numbers
  • Military ID Numbers
  • Passport Numbers
  • Individual National Provider Identifier


Miscellaneous Identifier Workflow Example

As these Miscellaneous Identifiers are increasingly collected, they are useful on their own or along with Enterprise Identifiers in improving probabilistic Patient Matching as described elsewhere in this IG.

Authorized Representatives

There are two primary actors that engage in the process of requesting health data from an external source:

  • Patient – the subject of the data query being sent in the $match request (or equivalent)
  • User – The individual who is being authenticated to initiate a $match request (or equivalent)

The Patient and the User may not be the same individual in a transaction. An individual who has been authorized to access another individual’s health data is called an Authorized Representative. Instances where an Authorized Representative is present include, but are not limited to:

  • B2B Use Cases – A physician accessing a patient’s health data through an HIE/QHIN query via their EMR
  • B2C Proxy User Use Case – An authorized representative is allowed to access a patient’s health record (e.g. a parent accessing their child’s records)

An authorized representative’s identity MUST be verified according to guidance and sufficient demographics MUST be collected if matching on the identity of the representative is to be performed, and at IAL 1.8 or higher if the match on identity will authorize access to data. In all cases the representative is, when local policies are met, authorized to access data on behalf of a patient prior to the query and determining authorization is outside the scope of this IG. The B2C workflow with credentials at the responding organization is already well-defined in the HL7 SMART App Launch IG.

Need a technical description and proofreading of the use case below:

Use Case Example with substitutable Identity Provider – Mary Smith is an authorized representative of her daughter, Jill Smith. Jill received care at General Hospital, which uses an EMR that gives patients access to their records through an app of their choice with FHIR. The hospital also uses an Identity Provider (IdP) for identity proofing and user authentication. Mary has not received care through General Hospital but has received care at another hospital that uses the same IdP. Mary would like to access Jill’s records at General Hospital. She requests Jill’s health data at the hospital’s FHIR endpoint using a registered app, which offers a variety of IdP options for authentication with trusted IdPs, including the IdP she already uses. Jill chooses this IdP and the hospital sends her to that IdP for authentication. Since she is already known by the IdP, she signs in; had she needed a new account, she could go through an authentication process to create the account. Once the IdP authenticates Mary, user profile information and authentication status is sent from the IdP to General Hospital, and the hospital can use a previously-recorded HL7 Identifier or demographics meeting patient matching requirements (matching on demograpics previously stored for Mary as a representative, in this case), to match on Mary’s identity as an authorized representative of Jill. If successful, the EMR gives Mary access to Jill’s data as Jill has authorized.

Organizational Identity

Organizational Identity as defined in this guidance is important for relying parties such as responders to use when considering the source of a data request (for example in an authentication token when initiated through a hub such as an HIE or a QHIN) to determine authorization, or to know the identity of a server or identity service–especially for the purpose of audit logging. When a transaction includes a claim of Organizational Identity in the digital certificate used to sign the claim or within another assertion such as a token request, the following details MUST be included:

  • Verified Legal Name of Organization responsible for data in the aspect of the transaction they are performing
  • OID assigned to that Organization (if any)
  • State where Organization was verified
  • Street Address verified for Organization (if information more granular than State is shared)