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.

The OBX segment is part of multiple message types that transmit patient clinical information. However this segment is most commonly utilized in ORU (Observational Report – Unsolicited) messages, and is sometimes utilized in ORM (Order) and ADT (Admit Discharge Transfer) messages. The OBX segment transmits a single observation or observation fragment, and can be used more than once in the message.

The fields in the OBX segment are as follows:

14SIOSet ID – Obx
22IDRValue Type
3590CERObservation Identifier
420STOObservation Sub-Id
565536STOObservation Value
710STOReference Range
85IDOY/5Abnormal Flags
102IDONature of Abnormal Test
111IDRObserv Result Status
1226TSOData Last Obs Normal Values
1320STOUser Defined Access Checks
1426TSODate/Time of the Observation
1560CEOProducer’s Id
1680XCNOResponsible Observer
1780CEOYObservation Method

*Note: For the complete HL7 Standard, please go to the HL7 organization website.

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:

M|||^^^^00000-0000|||||||86427531^^^03|SSN# HERE
OBR|1|8642753100013^LIS|20923085580^LCS|083824^PANEL 083824^L|||19980728083600|||||| CH13380|19980728000000||||||20923085580||19980730041800|||F
OBX|1|NM|150001^HIV-1 ABS-O.D. RATIO^L|||||||N|X
OBX|2|CE|001719^HIV-1 ABS, SEMI-QN^L||HTN|||||N|F|19910123|| 19980729155700|BN

NTE|1|L|Result: NEGATIVE by EIA screen.
NTE|2|L|No antibodies to HIV-1 detected.
NTE|1|L|NOTE: Submission of serum
NTE|2|L|separator tube recommended
NTE|3|L|for this test. Thank you
NTE|4|L|for your cooperation if you
NTE|5|L|are already doing so.

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