Understanding The Who and What of HL7
BY GRETCHEN BERRY
‘Our objective is to make computer systems in health care work better together,” stated Health Level Seven (HL7) Chair George Beeler, PhD. “If that happens, everyone benefits–patients, doctors and the people paying the bills.”
What Is HL7?
“HL7” is used to refer to both the non-profit organization based in Ann Arbor, MI, and the standard to which it is dedicated. The “Level Seven” portion of the name refers to the highest level of the International Organization of Standard’s reference model for communicating between computer systems. This model divides the communications process into seven layers or levels, with each layer adding different functions. At the lowest level are the physical considerations–the hardware necessary to convey messages. The seventh and highest level is the application layer, the actual exchange of information.
The HL7 standard is a series of protocols–instructions on how to organize and present information so that, for example, data from your HBOC computerized patient record can be sent to your 3M business system. “It’s sometimes referred to as interoperability,” explained Dr. Beeler. “The problem HL7 solves is how to exchange information in an unambiguous and timely fashion so that two systems that were not designed together can function together.”
To accomplish this, HL7 was developed as a flexible standard–meaning it can be tailored to suit each implementer’s needs. But that also means it is not “plug and play,” and does require some effort to analyze needs and configure vendor systems. However, the effort required to implement HL7 is far easier and less expensive than authoring a custom interface.
The HL7 messaging standard is, simply put, a blueprint. Formally titled, An Application Protocol for Electronic Data Exchange in Healthcare Environments, it tells programmers how to divide clinical data into segments (or packets) based on different message types. A message regarding an admission, for example, would include a message header (which defines its type and origin), patient identification, next of kin, etc. HL7 also specifies exactly what kind of information should be found in each of these segments and the suggested length. Patient identification, for example, should include the patient’s name, address and social security number. All data must be transmitted in the same manner and in the same order, so that both the sending and receiving systems know what is expected.
This mutually agreed upon format is the most widely accepted in the world, and its use is growing. Numerous vendors (including Cerner, SMS, Oacis and HBOC) now incorporate HL7 messaging in their products. As more hospitals merge and multisite health systems are formed, HL7 is becoming the way to ensure smooth data flow.
“Dealing with health care information systems is like changing a tire on a moving car,” observed Wes Rishel, vice chair of HL7’s Technical Steering Committee. “You can’t just scrap all your existing systems and start all over again. The challenge is finding a way to work with what you have. HL7 allows facilities to do that.”
Who is HL7?
HL7 was formed in March 1987, when dozens of professionals (including Rishel) gathered at a conference sponsored by the Hospital of the University of Pennsylvania to discuss how to make computers work better together. They published the first version of their messaging standard that October, and rather than rest on their laurels, immediately began work on Version 2.0. “We found that working on this interoperability problem was like peeling an onion,” offered Dr. Beeler. “Solving one problem reveals another layer you hadn’t thought about.”
Today, HL7 has approximately 1,500 members, some from as far away as Japan and New Zealand, and is accredited by the American National Standards Institute (ANSI). “ANSI accreditation means that you have some credentials behind you,” explained Karen Van Hentenryck, associate executive director of HL7. “It means that you meet their requirements for openness and consensus-building when it comes to developing and publishing standards. You have to submit to ANSI a copy of your by-laws and show that membership is open to anyone that is interested. There are stringent rules, such as the 60-day comment period. You must publish your standards and collect comments for 60 days. If anyone submits a negative comment during that period, you must prove that you made efforts to consider or address it.”
To help meet these consensus-building requirements, HL7’s membership is divided into 14 special interest groups (SIGs) and 14 technical committees. There is, for example, a technical committee devoted to medical records. This group consists of vendors, providers, consultants and others who make sure that the HL7 standards take into account all pertinent aspects of the medical record. The technical committees actually write the standards based on recommendations from the SIGs. Once the standards have been authored, they are voted on by the HL7 membership.
In the past few years, the focus of these groups has expanded beyond the messaging standard (which is currently in version 2.3.1). For example, another standards organization, the Clinical Context Object Workgroup (CCOW) recently joined HL7 as the Visual Integration Special Interest Group (VISIG). “CCOW started as a consortium of vendors and providers interested in bringing health care integration standards to the clinical desktop,” explained Robert Seliger, chief executive officer of Sentillion Inc. and co-chair of VISIG. “In November 1998, it became clear that CCOW needed to find a way to sustain itself financially and logistically. We decided to approach HL7 because of its fine reputation. Joining HL7 has been a win-win situation. We got the advantages of HL7’s infrastructure and they got an organization that understood the fine art of writing readily implemented component software standards.”
CCOW’s work has centered on integrating desktop applications to help users access information more quickly. They have developed the Patient Link standard, which enables users to select the patient of interest once, from any application, as the means to automatically “tune” all of the applications to the same patient. They have also developed the User Link standard, which grants users access to a range of applications, but only requires them to sign on once. Both the Patient Link and User Link standards have been approved by the HL7 membership and are awaiting approval by ANSI.
Another effort new to HL7 is the Arden Syntax. The American Society of Testing and Materials (ASTM), in response to requests from its members and members of HL7 to consolidate their efforts, recently transferred all Arden Syntax copyrights and future initiatives to HL7. “The Arden Syntax Technical Committee is a group of people interested in using the computer to assist in decisions and send reminders,” elaborated Rishel. “For example, if you put a patient on a diuretic, it can lower their potassium level, which can stop their heart. Normal protocol is, if you change a patient’s diuretic level, you want to do blood work to determine their potassium level. Arden Syntax efforts concentrate on creating a standard way for a physician’s computer to automatically issue a reminder to have that blood work done when information about a change in diuretic levels is input.” Already being incorporated into large vendor systems, the Arden Syntax for Medical Logic Modules is awaiting ANSI approval.
Stan Huff, MD, HL7’s chair-elect, co-chairs another important component of HL7–the vocabulary technical committee. “Clinical vocabularies play an essential role in making HL7 messages consistent and understandable between implementations,” Dr. Huff explained. “People have used HL7 messages so that everything has the same format, but they used different vocabularies. That’s like having a phone where the person on one end speaks French and the person on the other speaks English. The carrier system works great, but no one can understand anything.”
To correct this problem, the committee has been working to map connections between the various vocabularies in use. “We’re trying to be fair to all the vocabularies out there,” said Dr. Huff. “We aren’t creating a new vocabulary, we are just trying to establish relationships between terms and to use the existing vocabularies more efficiently.”
HL7 also recently added a group dedicated to exploring and capitalizing on the potential of Extensible Markup Language (XML). A way of formatting information used on the Web and in intranets, XML allows users to define “tags” to express the structure of a database, relationships between objects and the structure of information in documents. (For more on XML, see ADVANCE, July 5, 1999.)
“XML is a way to get context into the document and make it more precise,” stated Rishel. “It allows the same file to be marked up for multiple purposes. It allows for more complex searches, calculations and decisions. Furthermore, if you want your information systems to be able to work on data that are collected on the Web, they all have to agree on a common format, and we think that format will be XML.”
These are only a few of HL7’s current efforts, and the number and type of standards it seeks to create is certain to grow. “All of our newer efforts basically center around enhancing our existing standard,” noted Dr. Beeler. “Our overall goal is to reduce the effort needed to bring two systems together.”
It is a goal that health information management (HIM) professionals can play a valuable part in reaching. “We would love to see more participation from provider organizations,” stated Dr. Beeler. “We are always interested in expanding the base of expertise from which we draw.” Van Hentenryck agreed, adding, “We try to balance the interests of all concerned–the people who are developing the computer systems and the people who are using them. We want to make sure that everyone has a voice. There are actually a lot of people with little or no technical expertise participating in HL7, so don’t be intimidated. We encourage anyone with an interest to join.”
The next HL7 plenary and working group meeting is scheduled for September 27 through October 1, in Atlanta. For more information about HL7, visit their Web site at www.HL7.org. *
Gretchen Berry is an assistant editor at ADVANCE.
