Health Information Exchanges (HIEs): Emerging Architectural Patterns

The following are some emerging architectural patterns in the nascent field of HIEs:

• Decentralized and Hybrid Models utilizing a service-oriented architecture (SOA). A centralized registry stores metadata about the type and location of clinical data available in edge systems connected to the HIE. For privacy and security reasons, the clinical data itself is kept at its source as opposed to a centralized repository. Upon request, a Record Locator Service (RLS) finds the data in edge systems and securely routes the data to authorized requestors.
  
  
• A Data Use and Reciprocal Support Agreement (DURSA) provides the legal framework for participation in the HIE.
  
  
• Use of a master patient index (MPI) as a core infrastructure for patient matching. The MPI stores identifying information on all patients with records in participating systems.
  
  
• Use of Integrating the Health Enterprise (IHE) profiles such as Patient Identity Cross-Reference (PIX) and Cross Enterprise Document Exchange (XSD.b) to facilitate patient discovery and the query and retrieval of clinical documents.
  
  
• Health Information Event Messaging to provide the ability to subscribe to health information.
  
  
• Interoperability with NHIN Exchange to enable exchange of data with other state and federal agencies such as the Department of Veterans Affairs (VA) and the Department of Defense (DoD). This requires support for NHIN messaging standards such as the Web Services Interoperability (WS-I) Profiles WS-I Basic v 2.0 and WS-I Security v 1.1. WS-I Basic specifies the use of SOAP 1.2, WSDL 1.1, WS-Addressing 1.0, WS-Policy 1.5 , MTOM 1.0 , and UDDI v3.0.2 for the NHIN Web Services Registry. WS-I Security defines the security standards for NHIN Exchange including TLS, AES 128, X.509, XML D-Sig, and Attachment Security. NHIN has adopted an authentication and authorization framework based on SAML 2.0.
  
  
• Use of the HL7 Continuity of Care Documents (CCD) as the data exchange standards for clinical documents. Meaningful Use criteria allow the ASTM CCR specification as well.
  
  
• Health Record Banks (HRBs) containing Personal Health Records (PHRs) as participating nodes in the HIE. The HRBs allow patients to exercise control over their health records by granting permissions to specific providers to view those health records.
  
  
• Ability to connect to the HIE through a local EMR or a web-based portal (for example to allow access for physicians without an EMR).
  
  
• For simple and secure interoperability, the NHIN Direct draft proposal at the time of this writing is to use:
  
  
  
  
  • SMTP as a backbone protocol
    
  • S/MIME-signed and encrypted messages for security
    
  • IHE XDM for content and metadata packaging
    
  • IHE XDR, REST, and Email (POP/IMAP) as edge protocols
    
  • TLS (with a server certificate only) for on-the-wire security
    
  • XDR as the backbone for NHIN Exchange.