Health Level 7 (HL7)

Intro to Health Level 7 (HL7)

Health Level Seven (HL7) is the most successful messaging standard in the healthcare industry, not only in North America, but all around the world.
Formed in the United States in 1987, HL7 has the mission of developing an international set of open standards for data format and content that allows health information systems to easily and effectively communicate with one another.
Health Level 7 (HL7) is a term used to refer to the all-volunteer, not-for-profit organization, Health Level Seven, Inc., which is involved in development of international healthcare standards. HL7 is also used to refer to some of the specific standards created by the organization. HL7 and its members are dedicated to providing a comprehensive framework (and other related standards) for the exchange, integration, sharing and retrieval of electronic health information. These standards, which support clinical practice as well as management,delivery, and evaluation of health services, are the most commonly used in the world.

Goals and Basic Tasks of HL7

To provide - global - standards for the exchange, management, and integration of data that supports clinical patient care and the management, delivery, and evaluation of healthcare services.
Specifically, to create flexible, cost effective approaches, standards, guidelines, methodologies, and related services for interoperability between healthcare information systems.
Interoperability: The ability of two or more systems or components to exchange information (Functional interoperability) and to use the information (Semantic interoperability) that has been exchange.

HL7's purpose is to make easy the communication in healthcare settings. The primary goal is to provide standards for the data exchange among healthcare computer applications that eliminate or reduce the custom interface programming and program maintenance that may otherwise be required. This goal can be delineated as a set of goals:

Develop coherent, extendible standards that permit structured, encoded health care information of the type required to support patient care, to be exchanged between computer applications while preserving meaning.
Develop a formal methodology to support the creation of HL7 standards from the HL7 Reference Information Model (RIM).
Educate the healthcare industry, policy makers, and the general public concerning the benefits of healthcare information standardization generally and HL7 standards specifically.
Promote the use of HL7 standards world-wide through the creation of HL7 International Affiliate organizations, which participate in developing HL7 standards and which localize HL7 standards as required.
Stimulate, encourage and facilitate domain experts from healthcare industry stakeholder organizations to participate in HL7 to develop healthcare information standards in their area of expertise.
Collaborate with other standards development organizations and national and international sanctioning bodies (e.g. ANSI and ISO), in both the healthcare and information infrastructure domains to promote the use of supportive and compatible standards.
Collaborate with healthcare information technology users to ensure that HL7 standards meet real-world requirements, and that appropriate standards development efforts are initiated by HL7 to meet emergent requirements.

A Brief History of HL7...

1987: Interested users in the United States start work on a standard - "Health Level 7".
1990: First standard (V2.1).
1993/94: First International Affiliates join.
1994: HL7 becomes, American National Standards Institute, ANSI-accredited.
1997: The Department of Health acknowledges HL7 as the healthcare messaging standard.
2000: HL7 V2.4 released with support for Australian requirements and XML encoding.
NOTE: More than 93% of all organisations in the U.S. with Health IT systems use HL7!

Why Health Level "SEVEN"?

The Open System Interconnection (OSI) model divides the functions of a protocol into a series of layers . Each layer has a property that only uses the functions of the layer below it, and exports functionality only to the layer above it. A system that implements protocol behavior consisting of a series of these layers is known as a 'protocol stack' or 'stack'. Protocol stacks can be implemented either in hardware or software, or in a combination of both. Typically, only the lower layers are implemented in hardware, with the higher layers being implemented in software.

For further information about OSI, please click on image.

7. Application <--- HL7
6. Presentation
5. Session
4. Trasport
3. Network
2. Data Link
1. Physical

HL7 and OSI Model

In more detail, "Level Seven" refers to the highest level of the International Organization for Standardization (ISO) communications model for Open Systems Interconnection (OSI) - the application level. The application level addresses definition of the data to be exchanged, the timing of the interchange, and the communication of certain errors to the application. The seventh level supports such functions as security checks, participant identification, availability checks, exchange mechanism negotiations and, most importantly, data exchange structuring.
On the other hand, HL7 does not specify a set of ISO approved specifications to occupy layers 1 to 6 under HL7's abstract message specifications. HL7 does, however, correspond to the conceptual definition of an application-to-application interface placed in the seventh layer of the OSI model.

Background and Organizational Structure

The HL7 organization has grown from a modest 14 members in 1987, to over 2200 members worldwide including 500 corporate members today, which includes International Affiliates in 33 countries. These members share a commitment to the development and advancement of clinical and administrative standards in healthcare. Using a well-defined set of operating procedures, HL7's members - including vendors, providers, consultants and payers - have information technology expertise in all segments of the healthcare industry. Collectively, they develop the standards designed to increase the effectiveness, efficiency and quality of healthcare delivery.
Members of Health Level Seven are known collectively as the Working Group, which is organized into technical committees and special interest groups. The technical committees are directly responsible for the content of the Standards. Special interest groups serve as a test bed for exploring new areas that may need coverage in HL7's published standards.

Why Standards?
- Health care information is increasingly transmitted ellectronically.
- For Healthcare IT systems to exchange information, they can either communicate via custom interfaces OR share a common date format.
- A common data format is cost-effective, but needs up-front agreement and commitment = "a Standard".
Note: Some examples of standards that we are using today are the mobile phones ("GSM"), CDs ("ISO"), ATMs etc.

The Importance of HL7

Hospitals, doctors, and other healthcare facilities around the world require the ability to send and receive heathcare data, including patient information and various lab reports. As a result, vast amounts of healthcare information are exchanged on a daily basis. However, medical data can be extremely complicated due to the abundance of clinical terminology, as well as the structural complexity in the formation of the presented information. Thus, this information must be presented in a standardized format in order to ensure that the data is universally understood and organized. In order to achieve this, all healthcare information must be sent in a specialized healthcare language.
The language that has been developed to overcome these obstacles is HL7. The HL7 protocol was developed by the Health Level 7 Organization. This consists of grammar and vocabulary that is standardized so that clinical data can be shared amongst all healthcare systems, and easily understood by all. By using the HL7 messaging protocol as a standard, all systems following the HL7 specifications are able to communicate easily with one another, without the need for information conversion.

Sample HL7 Message:

MSH|^~\&|EPIC|EPICADT|SMS|SMSADT|199912271408|CHARRIS|ADT^A04|1817457|
EVN|A04|199912271408|||CHARRIS
PID||0493575^^^2^ID 1|454721||DOE^JOHN^^^^|DOE^JOHN^^^^|19480203|M|
NK1||CONROY^MARI^^^^|SPO||(216)731-4359||EC|||||||||||||||||||||||||||
PV1||O|168 ~219~C~PMA^^^^^^^^^||||277^ALLEN FADZL^BONNIE^^^^||||||||||

To learn more about the specific componenets of an HL7 message and for a more thorough and
technical understanding of the HL7 messaging protocol, visit HL7 online manual.

As you can see, HL7 messages are NOT pretty. HL7 messages are having several problems, such as:
a) The vertical bar format for HL7 messages is idiosyncratic. This does not serve to connect medical informatics to the larger world of information technology.
b) The message format cannot be easily interpreted by reading the message ( NOT user friendly ).
c) Changes in HL7 cannot be incorporated easily into clinical information systems using older versions of HL7. Every hospital uses a slightly different variation of the HL7 "standard."
The solution for these kind of problems is Extensible Markup Language, also known as XML .

About XML:

Health Level Seven has been actively working with XML technology since the formation of the SGML/XML Special Interest Group. The SGML/XML group has evolved into two separate groups:

the XML Special Interest Group - which supports the HL7 mission through recommendations on use of Extensible Markup Language (XML) standards for all of HL7's platform- and vendor-independent healthcare specifications.
the Structured Documents Technical Committee - which support the HL7 mission through development of structured document standards for healthcare.
Both of these groups have produced work items that have been ratified by the HL7 membership.

Such innovation has allowed for everything from the availability of a patient's online medical record to a pharmacy's formulary to be represented and exchanged in an HL7 XML document. In fact, the HL7's Patient Record Architecture in (message standard) version 3.0 allows for a common format for exchanging a patient's medical record between different hospital systems or even different hospitals. This HL7 standard has thus come to serve as a foundation for the universal electronic medical record.
The scope of HL7's progressive activities is not limited to the electronic medical record. Recent activities and standards of HL7 have included modeling and methodology, vocabulary, clinical decision support, financial management, administration, regulated clinical research and information management, scheduling and logistics, clinical guidelines, community-based health, government projects, medication, security and accountability, templates, XML, and public health and emergency response.
HL7 has allowed for the interoperability between electronic Patient Administration Systems (PAS), Electronic Practice Management (EPM) systems, Laboratory Information Systems (LIS), Dietary, Pharmacy and Billing systems as well as Electronic Medical Record (EMR) or Electronic Health Record (EHR) systems. HL7 encompasses the complete life cycle of a standards specification including the development, adoption, market recognition, utilization, and adherence.