Intersection with Exchange

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The Direct Project / Nationwide Health Information Network Exchange Interoperability (Karen's Cross)

When looking at how NwHIN Exchange and the Direct Project can interoperate, Karen Witting presented the following use cases as fundamental to the problem (see diagram below for context):

a) Dr. D. Source wants to use Direct Project protocols to send to an entity serviced through NwHIN Gateway B
b) An entity serviced by NwHIN Gateway A wants to send information to Dr. D Destination

Each sending and receiving entity uses their local protocols to communicate with their local NwHIN Gateway or HISP.
The problem to be addressed is the definition of the transactions depicted by the red arrows at the center of the diagram.

(Please note that "NHIN Direct" has been renamed to "The Direct Project", and "NHIN Exchange", to "Nationwide Health Information Network Exchange."


So we simplify the problem to:
a) HISP A sends to NwHIN Gateway B
b) NwHIN Gateway A sends to HISP B

There are several possible models, including:

  1. Require all NwHIN Gateways to implement the HISP to HISP protocol
  2. Adopt NwHIN Exchange Document Submission protocols for HISP to HISP exchange

Regardless of the model, the transformation of three things is required:

  1. Transport - use of particular transport protocol (SOAP/REST/SMTP). These are fairly clear transformations and are considered relatively easy to implement
  2. Trust - transformation of trust models. Complexity is not yet clear as trust model for NHIN Direct has not been completely identified
  3. Metadata - needs detailed comparison and discussion to be able to see how far apart the two models are.
Note that both the Direct Project and NwHIN Exchange are content neutral so no transformation is necessary, although there may be issues in content exchange because some NwHIN Exchange partners may want to restrict the types of content they will accept.

Metadata Transformation
A detailed comparison and discussion regarding requirements for metadata is needed to understand how far apart the desired Direct Project metadata is from that desired by NwHIN Exchange. At a general level the differences seem fairly easy to resolve except for patient identification. NwHIN Exchange requires a patient identifier which is directly in conflict with the unwritten rule that users of the Direct Project don't have to worry about identifying the patient. Maybe NwHIN Exchange could adjust to accept patient demographics instead of an identifier, but even that isn't assumed available in the Direct Project. Identifying the right patient in a large enterprise is challenging to say the least and at this point this problem seems to be the biggest challenge in supporting Karen's Cross.