Why Interoperability Standards Matter to Nursing
When a patient transfers from a community hospital to a rehabilitation facility, their medication list, allergy record, and nursing assessments need to follow them — accurately and immediately. The technical infrastructure that makes this possible depends on healthcare data standards. HL7 and FHIR are the two most important standards in this space, and nursing informatics professionals need a working understanding of both.
What Is HL7?
Health Level Seven (HL7) is a nonprofit standards development organization founded in 1987. The "Level Seven" in its name refers to the seventh layer (application layer) of the ISO Open Systems Interconnection (OSI) model — the layer at which health information is exchanged between software applications.
HL7 produces the standards, not the software. Their standards define how clinical data should be structured and transmitted between systems. The most widely deployed HL7 standard in hospital environments is HL7 Version 2 (v2), which has been used for decades for messaging between EHRs, lab systems, pharmacy systems, and ADT (admission-discharge-transfer) notifications.
HL7 v2 in Practice
If your hospital sends an automatic message to the pharmacy system when a nurse enters a new medication order, that message is almost certainly an HL7 v2 message. V2 messages are pipe-delimited text strings that look arcane but are robust and widely supported. The challenge: v2 is highly customizable, which means two systems using "HL7 v2" can still be incompatible without custom interface work.
HL7 v3 and CDA
HL7 v3 introduced a more rigorous, XML-based approach. From v3 came the Clinical Document Architecture (CDA), which structures clinical documents (like discharge summaries and care plans) in a standardized, human- and machine-readable format. CDA is still in use, particularly for Continuity of Care Documents (CCDs) shared between providers.
What Is FHIR?
FHIR (Fast Healthcare Interoperability Resources, pronounced "fire") is HL7's modern interoperability standard, developed from the ground up for the internet age. Released as a draft standard in 2014 and maturing through subsequent versions (the current published standard is FHIR R4), FHIR takes a fundamentally different approach:
- Resource-based — Clinical data is broken into modular "resources" (Patient, Medication, Observation, Condition, etc.) that can be requested and combined independently.
- REST API-based — FHIR uses the same web architecture that powers modern apps, making it far easier for developers to build healthcare applications.
- JSON and XML support — Data can be exchanged in formats familiar to modern developers.
- Built for app development — The SMART on FHIR framework enables third-party apps to launch within EHR systems and access patient data securely.
How FHIR Is Changing Nursing Informatics Practice
Regulatory Mandates
The 21st Century Cures Act and CMS Interoperability Rules (effective 2021) require hospitals and payers to make patient data accessible via FHIR APIs. This is not optional — it is federal policy. Nursing informatics professionals need to understand FHIR to participate meaningfully in compliance planning and EHR optimization work related to these mandates.
Patient-Facing Apps
FHIR enables patients to connect third-party health apps (like Apple Health) directly to their EHR data. Nurses working in patient education and engagement will increasingly encounter patients who arrive with data pulled from these apps. Understanding the source and limitations of this data matters for clinical interpretation.
Clinical Decision Support Hooks (CDS Hooks)
CDS Hooks is a FHIR-based standard for triggering external clinical decision support services from within an EHR workflow. When a nurse opens a patient's chart or enters an order, a CDS Hook can call an external service — including AI-powered tools — and display the result as a card within the EHR interface. Understanding this architecture helps nursing informaticists evaluate and implement modern CDS tools.
A Quick Comparison
| Feature | HL7 v2 | FHIR R4 |
|---|---|---|
| Age / Maturity | Established since 1980s | Modern standard, stable since 2019 |
| Format | Pipe-delimited text | JSON / XML over REST APIs |
| Primary Use | Internal hospital messaging | External data exchange, app development |
| Developer Friendliness | Requires specialized expertise | Accessible to web developers |
| Regulatory Requirement | No current federal mandate | Required by 21st Century Cures Act |
What You Should Do With This Knowledge
You don't need to become a software developer to work effectively in nursing informatics, but you do need to:
- Understand enough about HL7 and FHIR to communicate effectively with IT teams and vendors.
- Recognize when an interoperability problem is a standards issue versus a configuration issue.
- Advocate for FHIR-based data access when evaluating new technologies.
- Stay current as FHIR R5 and subsequent versions introduce new capabilities.
Healthcare interoperability is one of the most consequential infrastructure challenges in modern medicine. Nursing informaticists who understand the standards landscape are uniquely positioned to bridge clinical needs and technical solutions.