Health information exchange architectures

The correct answer: A. Federated (decentralized)

✅ Why this answer

In a federated architecture, data stays at its source. The exchange holds only:

• A patient index, to know it is the same patient across hospitals.
• A record locator, to know where their data is.

On request, the exchange queries the hospitals concerned and assembles the response immediately. This reassures hospitals that want to keep control of their data.

❌ Why the other options are wrong

• (B) Centralized: data is copied from all participants into a single central repository. This is what the hospitals rejected.
• (C) Hybrid: combines the two approaches; some data is stored centrally (such as results or summaries) and the rest stays at the source. The question says the exchange stores no clinical data.
• (D) Point-to-point interfaces: not a regional exchange architecture; the number of interfaces grows rapidly with every new participant (n(n−1)/2), and there is no shared index.

💡 Key concept

• Centralized: faster response and easier analytics, with greater concern about control, privacy and the cost of the repository.
• Federated: more control for participants, with dependence on their systems being available at query time.
• Hybrid: a balance between the two.

In every architecture, patient matching remains a core challenge, since the United States has no single national identifier.

In the exam: “data stays at the source” + “only an index and a record locator” + “real-time query” = federated. “A copy of the data in a central repository” = centralized.

🔗 Related facts and questions

• The components of an exchange network: the master patient index (MPI), which decides that different records belong to the same person; the record locator service (RLS), which knows where that person’s records are; the provider directory for finding providers’ addresses, management of patient consent, and an audit log of every access.
  Practice question: a patient is registered as “Mohammed Ahmed Ali” at one hospital and as “Mohd Ali” with the same birth date at another. Both hospitals’ systems are running, yet a query through the exchange returns only the first hospital’s records. Which component most likely failed? → The master patient index (MPI): it did not link the two registrations to one person.
• The effect of the architecture when a participant is down: in a federated architecture, if one hospital’s system is down at night for maintenance, its records reach no one until it is back. A central repository stays available because it holds a copy.
  Practice question: emergency departments complain that records are missing whenever a hospital’s system is down. The participants agree to send a summary of each visit (allergies, medications, problems) for the exchange to store, while the full record stays at the source. What does the architecture become? → Hybrid.
• Patient consent models: under opt-out, the patient’s data are shared unless they object. Under opt-in, they are shared only after explicit consent. The first makes the network richer in data; the second gives the patient more control but reduces participation.
• The three forms of exchange: directed exchange pushes information to a known recipient. Query-based exchange searches for a patient’s records held by others, as in this question. Consumer-mediated exchange is where the patient gathers their own data.
• IHE (Integrating the Healthcare Enterprise) standards for document sharing: the XDS (Cross-Enterprise Document Sharing) profile rests on a central registry that knows where each document is stored. The XCA (Cross-Community Access) profile allows queries across different exchange communities. The PIX (Patient Identifier Cross-referencing) profile links one patient’s identifiers across organizations, and the PDQ (Patient Demographics Query) profile finds a patient by demographic data.
• Who joins a health information exchange first? a related question in the full bank.
• Portability of health information across networks: "Health information portability through exchange networks" (in the full bank).
• Probabilistic patient matching: "Probabilistic matching in the master patient index" (in the full bank).
• Connecting networks at the national level: "The Trusted Exchange Framework and Common Agreement (TEFCA)" (in the full bank).