What Is HL7?

Background

Just as people from different countries with completely different native tongues are only able to communicate with each other if they can speak a common language, healthcare computer systems can only share clinical information if they communicate in a common way. Before people or computers can share clinical data with one another, they must both:

  • Have functions to be able to physically communicate, e.g. speak & hear or send and receive documents and data files, share data and information (this is called “functional interoperability”).
  • Speak a common language (in terms of nouns, verbs, grammatical structure etc) and share the same vocabulary that allows them to understand complex medical conditions and processes (this is called “semantic interoperability”).

Because hospital computers were not able to “understand” each other, a group of healthcare computer systems users in 1987 started developing a common “language” which they named “Health Level 7”. Over time, the HL7 interoperability protocol became a nationally and then globally accepted standard.

The issue of connecting healthcare computer systems is not an easy one. While exchanging clinical data between two computers is trivial, the complexity grows exponentially as the number of systems increases. It quickly becomes evident that it is impossible to fund and build custom interfaces to interconnect the thousands of computer systems typically found in a large State or Territory health department.

The term “Health Level 7” is used for both the organisations involved in developing and supporting the healthcare standards as well as for the standards themselves. Best known are the Version 2.x and Version 3 inter-computer messaging standards developed by HL7 (which has local organisations in 30 countries), but HL7 also creates international standards for decision support (Arden, GLIF & GELLO), Electronic Health Records (EHR), clinical text document mark-up (CDA) and, user interface integration (CCOW).

What Does The Name “HL7” Mean?

“Level Seven” refers to the upper-most level of the International Standards Organisation’s (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.

The HL7 Organisation

The Health Level 7 organisation is a global, volunteer not-for-profit community of healthcare informatics experts and information scientists collaborating to create standards for the exchange, management and integration of electronic healthcare information.

HL7 Standards

The HL7 standards enable the interoperability between electronic Patient Administration Systems (PAS), Hospital Information Systems (HIS), Laboratory Information Systems (LIS), Dietary, Pharmacy, Radiology and Billing systems as well as Electronic Medical Record (EMR) or Electronic Health Record (EHR) systems.

The HL7 standards have found wide acceptance around the world. In Australia, the US, Canada and New Zealand, the healthcare systems heavily use HL7 messaging. In 1998, the US reported that over 95% of all healthcare organisations were using HL7. New Zealand has for many years based its health services records on a national patient identifier - accessed using HL7.

Australia is also a heavy user of HL7 - about 50,000 HL7 V2.x messages probably have been exchanged between Australian computer systems since you started reading this article!

Interestingly, Australia has been a global leader in the acceptance of HL7 by governments: In March 1997, the then Health Minister Michael Wooldridge launched the first Australian HL7 Standard. In August 2004, the National Health Information Group (NHIG), an expert committee established by the Australian Health Ministers to provide guidance on national health information requirements and related technology planning, endorsed HL7 as the national standard for the electronic messaging of health information across Australia. In March of this year, the National eHealth Transition Authority (NEHTA) reaffirmed this endorsement.

HL7 Australia

In Australia, HL7 is officially represented by HL7 Australia, an open, volunteer-based, not-for-profit organisation that supports the needs of HL7 users in Australia. HL7 Australia is the local HL7 user group and the accredited national affiliate of HL7 Inc. (USA). It has local responsibility for a range of core activities including the distribution and licensing of the HL7 Standards materials, education and participation in HL7.

A frequent misconception about HL7 is that the group develops software. In fact, HL7's primary goal is to create flexible, low-cost standards, guidelines and methodologies to enable the exchange and interoperability of electronic health records. Such guidelines or data standards are an agreed-upon set of rules that allow information to be shared and processed in a uniform and consistent manner. These data standards allow healthcare organisations to easily share clinical information. It is hoped that this ability to exchange information will also help minimise the tendency for medical care to be geographically isolated and highly variable.

So How Does HL7 V2.X Work?

Essentially, HL7 conveys clinical information in a standard way between data stores in different computer systems. Data is formatted according to the HL7 standard rules, and then enveloped before it is sent out via a network to the destination system. V2.x messages have a variable-length, positional format and consist of lines (“segments”) of ASCII text. Each line of text is a fixed sequence of data elements (otherwise known as fields or data items) separated by delimiters. In the HL7 standards document, each data item is well defined. HL7 V2.5 contains approx. 1700 data items.

Each data element is usually separated by vertical bar (or pipe “|”) characters, may have components (separated by “^” characters) and may repeat (e.g. for multiple patient IDs, phone numbers etc).

HL7 V3

HL7 Version 3 is a next-generation HL7 messaging standard recently completed and now being implemented in some countries. Version 3 uses formalised modelling to improve the way it is defined and to attempt to make its content less ambiguous to the vendors implementing it.

The underlying model is known as the Reference Information Model (“RIM”) as a common source for the information content of specifications.

HL7 Version 3 is being implemented in the UK and in Canada. Initially the implementers were faced with many problems, but substantial changes have been made and most technical hurdles have been overcome. There are still questions however, if the move from V2.x to V3 can be justified on a cost/benefit basis.

HL7 For GPs And Specialists

HL7 is already allowing the electronic exchange of Pathology requests and reports between the labs and the doctor’s desktop software. Electronic Immunisation and Authority Drug approvals using HL7 messaging have been trialled. Electronic discharge summaries and referrals are currently in development. The technology is available and ready for these clinical events to occur paper-less, seamlessly integrated with the desktop practice management software and also automatically populating the patient’s medical record.

Posted in Australian eHealth

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