The OBX segment is primarily used to carry key clinical observation/results reporting information within report messages, which must be transmitted back to the requesting system, to another physician system (such as a referring physician or office practice system), or to an archival medical record system. In certain cases (such as ORM messages), the OBX segment may carry clinical information that might be needed by the receiving system to interpret the observation to be made, rather than actual information about observations and results.
OBX segments may, optionally, be followed by the NTE segment to provide notes and comments. In HL7 pipe and hat format, the OBX segments (shown in red below) would look like this in an ORU-R01 message. In this example, the first OBX segment does not have any notes or comments, while the next three OBX segments do: