The Role of Clinical Data Standards
Health information exchange depends on standardized formats and vocabularies so that disparate systems can share and interpret clinical data consistently. Health Level Seven International, known as HL7, has produced the dominant family of standards used in healthcare messaging and document exchange for decades.
HL7 Version 2
HL7 v2 is a pipe-and-hat delimited messaging standard first released in the late 1980s and still widely used today for real-time transactions such as admission, discharge, and transfer messages, lab orders and results, and pharmacy orders. Its flexibility allowed broad adoption, but that same flexibility created inconsistent implementations across vendors, requiring extensive interface customization.
HL7 Version 3
HL7 v3 was developed to address v2 inconsistency by using a Reference Information Model, or RIM, and XML-based messaging with more rigid structure. While technically more consistent, v3 saw limited adoption due to its complexity and the significant cost of migrating from established v2 interfaces.
Clinical Document Architecture
The Clinical Document Architecture, or CDA, is an XML-based document standard derived from the HL7 v3 RIM. CDA documents, such as the Continuity of Care Document, package structured and narrative clinical content into a single, human-readable and machine-processable file, commonly used for care summaries exchanged during transitions of care.
Fast Healthcare Interoperability Resources
FHIR represents the newest generation of HL7 standards, built around discrete data units called resources, such as Patient, Observation, Condition, and MedicationRequest. FHIR uses modern web technologies including RESTful APIs and JSON or XML formatting, making it far easier for developers to implement than prior HL7 versions.
Key FHIR Concepts
- Resources represent granular clinical concepts that can be combined as needed
- RESTful APIs allow standard create, read, update, and delete operations
- Implementation guides tailor FHIR for specific use cases, such as US Core
- SMART on FHIR enables third-party applications to securely access EHR data
Interoperability Framework Implications
Federal interoperability rules under the 21st Century Cures Act require certified health IT systems to support FHIR-based APIs, enabling patient access apps and provider-to-provider data exchange. HIM professionals should understand how these standards affect data governance, patient access rights, and information blocking compliance obligations across the organization.