Health interoperability standards serve to encode and exchange health information. Some, such as HL7 and DICOM, are well known, but there are many more. It is essential that we know the most important ones and when they are used, especially if we work in health informatics.

There are standards for messaging, terminology, and documents. Here we present them organized by categories, with links to other resources so that you can know all of them.

What is interoperability? #

First of all, we must be clear about what interoperability is. There are many definitions, but one of the briefest and most complete is from IE³:

Interoperability is the ability of two or more systems or components to exchange information and use the exchanged information.

IEEE

This definition tells us that interoperability is not the final goal, but a means to exchange and use information, which is what we really want.

Therefore, for our system to be interoperable it must:

• Be able to exchange useful information with the rest of the systems in a way that they can all interpret it.
• Be capable of using this information.

Luckily, we have the help of interoperability standards to integrate our systems and we already know the advantages of integrating systems in healthcare. But, before getting to know them, it is important to know what these standards actually are.

What are interoperability standards? #

In medical informatics there are more and more systems, applications, and devices. So, we may wonder: how can we ensure that the exchange of information is carried out correctly between our system and the rest?

Interoperability standards answer this question and each interoperability standard has an objective. Thus, the three main groups of health interoperability standards are:

• Messaging (or data exchange) standards like HL7 and DICOM.
• Terminology standards like SNOMED CT, ICD-10 (CIE-10), and LOINC.
• Document standards like CDA, CCR, and CCD.

Next, we will look at the main standards of each group.

Messaging Standards #

Messaging (or data exchange) standards are interoperability standards that ensure that information exchange between systems is carried out consistently. The most widely used are HL7 and DICOM.

The mission of messaging standards is to define instructions for the format, data types, and structures so that all systems have common rules for sharing clinical information.

The most important within this group are the DICOM and HL7 standard families.

HL7 #

HL7 provides a set of standards for exchanging, integrating, and retrieving electronic health information.

We will review the most prominent HL7 standards: HL7 version 2, HL7 version 3, and FHIR.

If you want to know more, we also have a guide with the most important HL7 standards.

HL7 V2 #

Version 2 of HL7 is the most widespread messaging standard for the exchange of clinical information between systems. It was published in 1987 and is aimed at providers of information technology and health services.

If you want more information and resources, you can read our guide on HL7 standards and the part related to HL7 V2.

HL7 V3 #

Version 3 of HL7 was launched in 2003 and is a very ambitious project within interoperability standards. HL7 V3 aims to cover all aspects of implementation: messaging, data types, and terminologies.

It is based on HL7 RIM (Reference Information Model). RIM is a model of reference objects of clinical data that identifies the life cycle of messaging within clinical activity.

HL7 V3 has a semantic approach and is more global, normative, and strict than version 2, which is more flexible and easy to implement. Perhaps for these reasons, it is not as widespread as version 2, although it is used in several public health services such as the United Kingdom, the Netherlands, and Canada.

You can also find more information in our guide on primary HL7 standards and its section on HL7 V3.

HL7 FHIR® #

FHIR^® is an interoperability standard that combines the best of HL7 V2, HL7 V3, and CDA. It uses web standards, such as XML and JSON, and focuses on facilitating implementation. In addition, it is free and we can use it without restrictions.

FHIR stands for Fast Healthcare Interoperability Resources because FHIR uses resources to represent real-world concepts such as patients, appointments, test results, etc. Through these resources, clinical and administrative procedures can be modeled more simply than with other alternatives.

In our guide on the most important HL7 standards, there is more information and resources about:

• The HL7 FHIR standard
• The resources in FHIR

DICOM® #

DICOM^® is the standard for exchanging medical images and integrating with RIS (Radiological Information Systems). DICOM stands for Digital Imaging and Communications in Medicine.

The DICOM standard allows us to handle, store, print, and transmit these types of images, making use of files (known as DICOM files) and communications based on TCP/IP protocols.

The standard is free and downloadable from the official website.

External resources on DICOM:

• Download the standard.
• Official page.

ASTM E1381 #

ASTM E1381, published by ASTM International, is a key messaging standard for clinical laboratories. It specifies a digital communication protocol for transmitting laboratory data between medical devices and Laboratory Information Systems (LIS). Based on the HL7 (Health Level 7) standard, ASTM E1381 provides a standardized framework for data exchange, ensuring interoperability and efficiency.

For a deeper dive into ASTM E1381, its benefits, and how it facilitates interoperability in your lab, visit our comprehensive guide on ASTM E1381.

Additional resources:

• Our guide on ASTM E1381 its usage and integration capabilities.
• Official page on ASTM site.

Terminology standards #

Terminology standards or controlled vocabularies ensure that the exchanged information is understandable by all systems.

These interoperability standards provide specific vocabularies for clinical concepts such as diseases, diagnoses, and medications.

The most important controlled vocabularies are:

• SNOMED CT: This nomenclature aims to identify all concepts that can be used in medicine.
• ICD-11: International classification of diseases. It is used mainly for statistics.
• LOINC: A classification of clinical observations widely used in laboratories.

SNOMED CT® #

SNOMED CT^® has the ambitious purpose of providing us with all the concepts that have ever been expressed in the field of medicine unambiguously, that is, without risk of confusion.

The acronym SNOMED CT stands for Systematized Nomenclature of Medicine – Clinical Terms. This terminology is maintained and distributed by SNOMED International (known until 2017 as IHTSDO).

Currently, it is the richest vocabulary that exists to code clinical findings, diseases, procedures, etc. And it covers the entire spectrum of the health domain thanks to its more than 300,000 concepts, along with the ability to combine and relate them.

Without a doubt, it will be much easier for us to integrate our system into any health environment, if we “speak and understand” SNOMED CT.

External resources on SNOMED CT:

• SNOMED International website.
• Browser of the standard by SNOMED International.

LOINC® #

LOINC^® provides a complete classification of clinical observations in medicine. It is especially used to code laboratory results, and we should use it if our application needs to communicate with LIS (Laboratory Information Systems).

LOINC® stands for Logical Observation Identifiers Names and Codes. And, since its creation, it has evolved and can now also be used to code physical examinations and other clinical observations.

External resources on LOINC:

• Official website.
• Tool to browse through the standard (free registration).

ICD-11 #

ICD-11 provides a complete classification and coding for diseases, as well as for a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances, and external causes of injury or disease. The number following the acronym is the version, therefore, ICD-11 is the 11th version of the classification, that was published in 2018 came into effect in 2022.

It is mainly used if we need to collect useful health information related to deaths, diseases, and injuries (mortality and morbidity), to communicate it to official bodies.

ICD-11 stands for International Statistical Classification of Diseases and Related Health Problems. The ICD is published by the World Health Organization (WHO).

Its Spanish version is also widely used: CIE-11 (Clasificación Internacional de Enfermedades). We should be familiar with it if our application needs to collect this type of information in Spanish-speaking hospital systems.

Links of interest about ICD:

• Official website.
• Standard content browser.

Clinical documentation standards #

We may think that messaging is enough to exchange information, but it is not, because documents and messages have different characteristics. Thus, documents:

• are objects whose exchange the healthcare professional is used to,
• have legal validity, as they allow the person responsible to sign,
• provide “complete” information to cover the associated medical act,
• are readable by human beings.

Examples of documents include discharge summaries, consultations, etc.

We can standardize the clinical information that our application is capable of generating and understanding using clinical documentation standards, for example: CDA, CCR, and CCD.

CDA® #

CDA^® defines a document for the exchange of clinical documents between systems, both in its structural and semantic part. A CDA document can contain any type of clinical document such as discharge reports, radiology test reports, or patient examination.

According to CDA, the six characteristics that a clinical document must have are: persistence, stewardship, potential for authentication, context, wholeness, and human readability.

CDA stands for Clinical Document Architecture. The first release of CDA, Release 1, was made available in 2000. However, in 2005, its second iteration, CDA Release 2 (or CDAR2), was introduced. This release was adopted as the ISO/HL7 27932:2009 standard for document exchange, solidifying CDA as one of the most important HL7 interoperability standards.

While the CDA can be utilized in a basic manner, its potential for reuse and interoperability increases significantly with the effort put into encoding document information employing vocabularies such as SNOMED-CT, ICD-10, LOINC, and others.

You can learn more about CDA and its document structure in our guide on fundamental HL7 primary standards and in its section on CDA.

CCD® #

CCD^® allows representing CCR data in a CDA XML. CCD is a joint project between HL7 and ASTM (American Society for Testing and Materials). Its acronym stands for Continuity of Care Document.

Links of interest about CCD:

• Standard page at HL7 International.

CCR #

CCR was a standard format for the communication of information. Its acronym stands for Continuity of Care Record.

The CCR standard was withdrawn on 2021.

HL7, FHIR, CDA, CCD, and their logos are registered trademarks of Health Level Seven International.
DICOM and its logo are registered trademarks of NEMA (National Electrical Manufacturers Association) for its standards publications relating to the digital communications of medical information.
SNOMED, SNOMED CT and SNOMED Clinical Terms and their logo are registered trademarks of SNOMED International.
LOINC and its logo are registered trademarks of Regenstrief Institute, Inc.