# HL7 vs. ASTM for lab instrument interfaces

How the two standards that connect lab instruments and systems differ, how messages actually move, and how to decide which one to use for each connection.

## What is the difference between HL7 and ASTM?

ASTM, maintained by CLSI as LIS1-A and LIS2-A2, is the long-standing standard for connecting analyzers to an LIS and often runs over RS-232 serial. HL7 version 2 is the dominant standard for exchanging orders and results between healthcare systems over TCP/IP, and many newer analyzers support it too.

## Is ASTM the same as CLSI LIS2-A2?

Yes. The ASTM E1381 and E1394 standards for instrument communication are now maintained by CLSI as LIS1-A, for low-level transmission, and LIS2-A2, for message content.

## Which HL7 messages are used for lab results?

Lab results are typically sent as HL7 v2 ORU^R01 messages, with results in OBX segments. Orders typically use ORM or OML messages, and receipt is confirmed with an ACK.

Read the full guide at https://labdynamo.com/hl7-vs-astm.