Get to the point: Understanding Health Level Seven (HL7)

This will be the first of a series of tutorials that will guide you to understand what is & how Health Level Seven (HL7 from now on) works.
Learning the HL7 messaging protocol standard can be a bit overwhelming, I will try to make it as easy as possible.

What is HL7?

HL7 is a messaging protocol standard used to exchange information between medical applications. Before HL7 was created, data exchange between medical applications required heavy integration development. The same code could not be used to communicate with other medical applications since there was no messaging protocol standard.

HL7 transmits one record of health-related information at a time. These messages may include patient records, billing info, etc.

How does HL7 work?

Let’s use the following example:

- A patient goes to the hospital and registers at the front desk. A new HL7 message is created and sent to the Hospital’s Information System (HIS).
- Once the doctor evaluates the patient, he decides to reschedule the patient for a next visit. A new HL7 message is created and sent back again to the HIS.

In this simple example we see that for every action a new HL7 message is created & processed. Since the patient has a unique identifier, the HIS can easily save the patient’s medical history.

What does an HL7 message look like?

An HL7 message is just a text message. Many newcomers might think that some sort of software is required to use HL7. HL7 is like any other protocol standard.

You will need to develop an application to receive and interpret the HL7 messages.

Example Message:

MSH|^~\&|GHH LAB|ELAB-3|GHH OE|BLDG4|200202150930||ORU^R01|CNTRL-3456|P|2.4
PID|||555-44-4444||EVERYWOMAN^EVE^E^^^^L|JONES|19620320|F|||153 FERNWOOD DR.^^STATESVILLE^OH^35292||(206)3345232|(206)752-121||||AC555444444||67-A4335^OH^20030520
OBR|1|845439^GHH OE|1045813^GHH LAB|15545^GLUCOSE|||200202150730|||||||||555-55-5555^PRIMARY^PATRICIA P^^^^MD^^|||||||||F||||||444-44-4444^HIPPOCRATES^HOWARD H^^^^MD
OBX|1|SN|1554-5^GLUCOSE^POST 12H CFST:MCNC:PT:SER/PLAS:QN||^182|mg/dl|70_105|H|||F

On my next tutorial I will teach you how to read these messages.