Patient Discovery (PD)

In order to share patient data among Nationwide Health Information Exchanges (NHIE) and other connected organizations, it is necessary to have mechanisms to match patient identities in the absence of a single national identifier. The Patient Discovery service meets this need by providing the mechanism for locating patients at other Nationwide Health Information Network-enabled organizations based on demographic information. The service provides the ability for one NHIE to determine whether other NHIEs have records for a given patient by submitting a set of demographic identifiers that NHIEs can use to match against their own master patient indexes.

A patient query is initiated from one NHIE to another to determine whether that patient is known to it. This query includes the patient ID and demographic information about the patient as it is known to the sending NHIE. The receiving NHIE in turn searches its patient index for matches, using the demographic information sent to it and its own matching algorithms, criteria, and policy. If a match is found, and sharing that patient ID over the Nationwide Health Information Network with the other NHIE is allowed by policy and patient preferences, the receiving NHIE sends its patient ID and the demographic information as it is known to that NHIE back to the querying NHIE. Finally, the querying NHIE compares the demographic information returned to it, using its matching algorithms, criteria, and policy, to determine whether it agrees with the match. Fundamental to the Patient Discovery service is that both NHIEs must agree on a match for an exchange to proceed. Authorization assertion(s) are included in the query message as specified by the Authorization Framework specification.

When queried for a match, an NHIE can return one of three response:

• Returns a match with a patient ID and demographics.
• Returns a message that there was an ambiguous match and request additional information that might result in a single matching patient.
• Returns no match, which might correspond to a failure to identify any matches or an ambiguous match to multiple patients when a more exact match cannot be expected.

An NHIE can only return multiple matches if they represent exact matches to multiple institutions within the NHIE that are believed to represent a single patient.

Patient Discovery also supports deferred processing. The deferred processing is basically the same with the exception that it can now be delayed after the initial request comes in. According to the Nationwide Health Information Network specifications, deferred processing introduces a new set of services on both the responding gateway and initiating gateway side. On the responding gateway, the service supports the receiving of a deferred Patient Discovery request message, and returns an application acknowledgment of the receipt of the message. At a later time, the responding gateway will process the request and send out the response on a waiting web service on the initiating gateway that is responsible for receiving these delayed responses. That service will send back an application acknowledgment that it has received the response. In gateway orchestrated mode, Patient Discovery must handle deferred processing in a slightly different way than other services. Under normal (non-deferred) circumstances, the gateway does most of the processing of a Patient Discovery message using some lower level calls to the adapter. But in the case of deferred processing, it is actually the adapter that should decide when the processing should start.