What is Health Level 7?

In this issue, IT World looks into HL7 (Health Level 7). We'll discuss what HL7 is and what it is not. We'll also talk about some of the major aspects of HL7 during our attempt to define it. There's a lot to talk about so let's get right to it.

What is HL7?

In general, Health Level 7 is a standard for information exchange between medical applications. It defines the format and the content of messages that applications use when exchanging data with one another under various clinical or administrative circumstances. It provides for "loosely-coupled" communication between independent and disparate applications, rather than a client/server relationship, for example, that is referred to as "closely-coupled."

HL7 does not describe how the data get from one place to another on a network-that's up to other protocols at the lower levels (see below). HL7 is a messageoriented structure designed to ensure that the meaning of the data gets across.

HL7 is also an event-driven protocol. This means that a specific event causes messages to be sent. For example, a patient being admitted to the hospital is an event that causes data to flow into the system to all areas that need to know about it. This is different from a client/server relationship, where data mainly flow when a client requests it.

The most extensively employed portion of the standard concerns messaging that facilitates dissimilar healthcare applications to exchange important sets of clinical and administrative data. We'll talk more about the messaging portion of the standard later.

The main thing to know or remember about HL7 is that it is a specification. Its development and management is controlled by a Standards Development Organization (SDO). The HL7 SDO is accredited by the American National Standards Institute (ANSI). Most SDOs produce standards. I've found that many times terms like standards, specifications, and protocols are commonly used interchangeably-don't let that throw you. There are specific definitions of these terms, but you'll find that they are used loosely in the literature.

The Health Level 7 organization is headquartered in Ann Arbor, MI. Like most other SDOs, it is a not-forprofit volunteer organization. Its membership consists of providers, vendors, payers, consultants, government groups, and those that have an interest in die development and advancement...