What is HL7

Here's an analogy that helps explain the purpose of HL7.   When you put together a sound system in your house, you typically pick the speakers that you like, the receiver that you like, etc.  All of those products can be from different vendors.   So, how do these components communicate with each other?  They communicate via RCA cable, HDMI cables or Optical cables.  HL7 is the RCA (HDMI or Optical) cable of the healthcare information system world.  It's what allows products from different vendors to talk to one another.

HL7 stands for Health Level Seven.  It allows disparate healthcare systems to exchange data in a common format.  Each HL7 transaction is comprised of segments.  Each segment is comprised of fields.  Each field can have multiple sub-fields.  HL7 defines, to a large degree, what data goes into which segment/field/sub-field combination.  That way, the receiving system knows where to look for specific data.

The most common types of data that get transmitted via HL7 include ADT (admissions, discharges and transfers), Orders, Results and Charges.  

Although HL7 segments contain well-defined fields, they also contain undefined fields.  The undefined fields allow vendors to put data into those fields, that don't belong anywhere else.  The issue becomes when vendors put data into those fields that actually belong in one of the well-defined fields.  This practice is commonly used by 'single source' vendors to make it difficult for other systems to communicate with their systems.   

HL7 Interface Engines can be very expensive products, but they allow remapping fields and massaging the data, in various ways, to make the data acceptable to the receiving system. A powerful and affordable HL7 Interface Engine is HL7Manager from Swearingen Software.

HL7 is not to be confused with DICOM.  HL7 is a data format standard whereas DICOM is an image format standard.  DICOM is used primarily by PACS systems to communicate with imaging devices and Modality Worklist Workstations.