Healthcare Information Systems and Interoperability
What the exam tests
This domain tests EHR and HIE architecture, interface engines, messaging standards, terminology mapping, patient identity, APIs, and interoperability policy. Know HL7 v2 messaging, FHIR resources and RESTful exchange, CDA documents, DICOM imaging, IHE profiles, and USCDI-style data classes.
Core rules
- HL7 v2 is widely used for event messages such as ADT; segments and fields carry patient, visit, and order data.
- FHIR models granular resources (Patient, Observation, Encounter) and supports RESTful APIs; it is not just a document format.
- CDA is a document standard; DICOM governs imaging objects and workflows.
- Semantic interoperability requires shared terminology and meaning, not only transport.
- Patient matching needs deterministic and probabilistic methods, with error handling and audit.
Worked example
An ADT A01 message must update an HIE. The interface analyst maps PID-3 (patient identifier list) to FHIR Patient.identifier, PV1-19 to Encounter.identifier, and PV1-44 to Encounter.period.start. Before go-live, test that the MRN system and assigning authority are preserved; otherwise two patients with the same local MRN may merge incorrectly. Define handling for missing identifiers, duplicate messages, and out-of-order updates. Log message IDs, acknowledgments, and errors. The reasoning: transport success is not semantic success; identity and encounter context must survive mapping.
Traps
- Assuming FHIR and HL7 v2 carry identical semantics.
- Matching patients on name and date of birth alone without governance.
- Ignoring acknowledgments and replay or error queues.
- Mapping local codes to standard terminologies without validation.