NeoTool — Singular Focus, Healthcare Integrated

Posted in HL7 Messaging, HL7 Standard

TCP/IP protocols mean that the data just starts coming in a stream, so how do you know where one HL7 message ends and the next one starts?

There is no set size. Some messages are quite concise, with a couple segments. Other HL7 standard messages are extremely long with repeating observation segments that contain an entire doctor’s report. Minimal Lower-Layer Protocol (MLP) is how you wrap an HL7 message with a header and footer to insure you know where a message starts, where a message stops, and where the next message starts.

These headers and trailers are usually non-printable characters that would not typically be in the content of HL7 messages.

The header is a vertical tab character <VT> its hex value is 0×0b.
The trailer is a field separator character <FS> (hex 0×1c) immediately followed by a carriage return <CR> (hex 0×0d)

It will look like this:

<VT> (hex 0×0b)

HL7 Message goes here

<FS> (hex 0×1c)

<CR> (hex 0×0d)

You may find that some clinical applications do not adhere to this standard. In these cases, it is extremely helpful to have flexible interface tools to adjust to the custom wrapping or no wrapping such that HL7 messages are properly recognized by your system.

Last 5 posts by Alex Lin

• What is an HL7 ADT Feed? - July 18th, 2008
• HL7 Minimum Layer Protocol (MLP) Defined - May 2nd, 2007