HL7 – A Standard That HealthCare Industry Speaks In

09 Nov

Each minute of our life is a lesson but most of us fail to read it. I thought I would just add my daily lessons & the lessons that I learned by seeing the people around here. So it may be useful for you and as memories for me…….

The article was written by VijayaLakshmi…

Guys!! Tired of reading technical stuff! Here is a piece of Health care messaging standard (HL7- Health Level 7)! Treat your knowledge buds!! Happy Reading!!


Real Time Scenario – HL7 need:

Marie is a CRF (Chronic Renal Failure) patient having her dialysis at Hospital X (Let’s assume!), seeking to have kidney transplantation at Hospital Y as the former is not providing it. When she visited Hospital Y for the registration, here is the conversation with Alan-Administrative staff of Hospital Y.

These challenges concern the inability to share and manage data within and across the healthcare organizations.

These can be overcome if organizations follow the same standards when setting up their information management systems. HL7 is that of standard.

What is HL7?

Health Level 7 – A healthcare specific communication standard for data exchange between computer applications.

Health Level 7, the ANSI standard for information interchange between foreign systems in the healthcare industry. The “7” refers to the fact that the protocol is designed to address the 7th layer of the International Standards Organization’s Open System Interconnect model (the application layer).  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.

Why HL7?

There are several health care standards development efforts currently underway throughout the world. Why then, embrace HL7? HL7 is singular as it focuses on the interface requirements of the entire health care organization, while most other efforts focus on the requirements of a particular department. Moreover, on an ongoing basis, HL7 develops a set of protocols on the fastest possible track that is both responsive and responsible to its members. The group addresses the unique requirements of already installed hospital and departmental systems, some of which use mature technologies.

HL7 Message Types and Versions:

There are four primary HL7 standard message types:

Messages type and function/ area of healthcare service get communicated.

  • Patient Administration (ADT) –Patient admission details (Demographics, visit, insurance…etc)
  • Orders (ORMs) – Orders to pharmacy/healthcare services
  • Results (ORUs) – Lab/diagnostic results from laboratory
  • Charges (DFTs) – Financial charges

HL7 organization takes care of message standards development. Any new versioning/ development commence from here.

Currently Version 2.1 to 2.7 is available. V2.7 is the latest release from HL7 organization. V3 is also available; since it is not backward compatible adoption of this is not very frequent!


HL7 Message Structure:

Each HL7 standard message (V 2.x) is composed of groups and segments where:

  • Groups contain segments or groups
  • Segments contain fields
  • Fields contain components
  • Components contain sub-components

Example HL7 Message (V 2.4):



PID||1112221212|HE1000044||JONES^SIMON^^^MR||19700912|M|||6 REDBOURNE ROAD^GRIMSBY^SOUTH HUMBERSIDE^^DN33 2UZ||01422 844745||32|2|RC|||||||||||||||01

PV1|1|1|B2^DPOW|11|1234||DONLA|G3413809||100|Do not cancel this patient||||||DONLA|I|||||||||||||||||||||DPOW||||||||||||V|G3413809^B81003

PV2||1|11|||||200609021000||4||Lap Chole||||||||||||||||||||||||


ZWL|20061124|Crocin|3|20110911|20110915|||Hep B|20111011|””||||01||||

In this example:

  • MSH, EVN, PID, PV1, PV2, AL1, ZWL – segments/groups
  • Each segment is unique on its data. For eg. PID passes only patient demographics, PV1 for patient visit, AL1 for allergies..etc
  • Each field in segment separated by delimiter. MSH segment has encoding characters (^~|&), application that’s ends data (HMS), application that receives data (SystemB)..etc fields.
  • Each field in segment can be denoted as MSH.1, MSH.2..etc
  • MSH.9 has the value ‘ADT^A05’. This is a composite field which has components ADT(Message Type) and A05(Message Name).Any subcomponent can be denoted as MSH.9.1 –ADT, MSH.9.2 –A05

Note: Version 3 HL7 is of a typical xml format.

HL7 interface architecture:

 Let’s say two healthcare systems A and B would like to have a HL7 interface for their communication needs. Here is the brief of it.

TCP protocol is used generally for HL7 messages communication. Apart from HL7, different formats of patient data (XML, text files, X12…etc) from desperate healthcare systems can be passed through HL7 interface and this can get the data in HL7 format to destination. Patient identity can be found by passing their SSN (Social Security Number) across applications.

Very own interfaces can be developed using industry dominant java/.net software. Yet there are many integration engines available. Mirth Connect, Biz talk, cloverleaf..etc are the well known HL7 interface engines available in the market.



Conclusion:  Health-Care is a sensitive domain where customer/patient’s expectations are very high and welfare is expected in no-time, it is very important how well the administration takes care of its robustness in communication. By considering this, practice of HL7 protocol needs to be implemented in a big way.


Please feel free to share your opinion, your relation, attachment with your father in your words  in the comments below.

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Posted by on November 9, 2012 in Technical


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