As health IT professionals, we read HL7 every day. Terms like PV1-5 and MSH-10 are second nature; however, ISA-15 and ST-3 might not be as familiar. These terms come from the X12 specification, which is heavily used in supply chain management (purchase orders, invoices, advance shipping notices, etc). X12 goes beyond supply chain, however, and defines document standards that are used by dozens of industries, including healthcare and finance.
The healthcare IT professional will likely encounter X12 in the form of two documents commonly used by finance and insurance: the 835 (Claim Payment) and the 837 (Healthcare Claim). Rather than HL7 message types (ADT,ORM) subdivided into Events (A01,O01), X12 is simply divided into transaction sets consisting of a three-digit number.
The biggest difference between X12 and HL7 stems from their different levels of concern.
HL7 lives in the day-to-day rapid movement of patients, medicines, and practitioners. One may not know all of the information about a given event all at once and, rather than wait until a complete story is formed, these tiny snippets of information are communicated as soon as they are known.
Because of this rapid-fire succession of small and incomplete pieces of information, when a message is received is almost as important as its contents. It is typically assumed that the most recent information is the most correct and so it is not uncommon to simply overwrite duplicated information with the most recent value.
X12 takes the opposite approach and looks at the transfer of information from the more macro-level. X12 transactions are not transmitted until all of the information about the event is known. As a result, each transaction typically stands on its own and does not depend on the transactions that came before or after. X12 is often delivered in large, hourly or even daily or weekly batches, rather than immediately being transmitted and waiting for an acknowledgement before sending the next message.
Even though the interfaces that handle both types of documents live side by side, keeping some of the high-level differences in mind when designing them can prevent lots of frustration.
HL7 is describing events that are likely happening now and depends on the near-instantaneous turnaround times that are measured in milliseconds. Thus, they are often tiny messages, only a few hundred bytes in length—the sound bites of the health IT world. X12 is more like the full-length, unabridged, annotated dissertation. But, thankfully, the expected turnaround is measured in hours or days.
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- Philosophical and Structural Differences Between HL7 and X12 - June 12, 2014