HL7 ORU Message: Observation Results

HL7 ORU (Observation Result Unsolicited) messages deliver clinical results from lab information systems (LIS), radiology information systems (RIS), pathology systems, and other diagnostic departments to the ordering provider’s EHR. The ORU^R01 is the primary trigger event — an unsolicited transmission of results without a prior query.

An HL7 ORU message is the message type that reports observation results — lab values, radiology findings, and pathology reports. “Unsolicited” means the sending system pushes results on its own schedule rather than answering a query. Each result group pairs an OBR segment (the test ordered) with one or more OBX segments (the individual values).

Segment	Name	Required	Purpose
MSH	Message Header	Yes	Sender, receiver, message type, version
PID	Patient Identification	Yes	Patient demographics and identifiers
PV1	Patient Visit	No	Visit context for the result
ORC	Common Order	Yes	Order control, placer/filler numbers
OBR	Observation Request	Yes	Test ordered, specimen info, ordering provider
OBX	Observation/Result	Yes	Individual result values (repeating)
NTE	Notes and Comments	No	Free-text comments on results
SPM	Specimen	No	Specimen type, collection time (v2.5+)

The OBR/OBX group repeats for each test ordered. A single ORU message can carry results for multiple orders.

The OBX segment carries individual observation values. The OBX-2 field specifies the data type:

Type	Name	Example Use
NM	Numeric	Lab values: glucose 98, WBC 7.2
ST	String	Text results: “Positive”, “Negative”
CE	Coded Entry	LOINC-coded results with display text
TX	Text	Multi-line narrative (radiology impressions)
ED	Encapsulated Data	Embedded PDF reports, images
FT	Formatted Text	Formatted narrative with escape sequences
CWE	Coded With Exceptions	v2.5+ replacement for CE
SN	Structured Numeric	Ranges and comparators: “>10”, “1:256”

Status	Meaning	Description
F	Final	Verified result, no further changes expected
P	Preliminary	Initial result, final pending
C	Correction	Previously final result corrected
A	Amended	Result amended after final
R	Entered (Not Verified)	Result entered but not yet reviewed
I	Pending	Specimen received, result pending
X	Cancelled	Order/test cancelled
W	Post Original as Wrong	Original result was wrong

A complete lab result message with multiple OBX segments:

Browse the full HL7 sample messages catalog for more ORU examples — each one ready to copy as valid HL7 or download as a .hl7 file.

Flag	Meaning
N	Normal
L	Below low normal
H	Above high normal
LL	Below lower panic limit (critical low)
HH	Above upper panic limit (critical high)
A	Abnormal
AA	Critically abnormal

Critical results (LL, HH, AA) typically trigger immediate notification workflows.

When a lab corrects a previously finalized result, the sending system transmits a new ORU^R01 with OBX-11 set to C (Correction). The receiving system must:

1. Match the corrected result to the original using the filler order number (OBR-3)
2. Update the displayed value
3. Maintain an audit trail showing both original and corrected values
4. Trigger provider notification for clinically significant corrections

Radiology and pathology systems often embed PDF or RTF reports in OBX segments using base64 encoding. The OBX-5 field contains the encoded document, and OBX-2 is set to ED (Encapsulated Data). The ED data type structure is: source^type^encoding^data — for example, ^APPLICATION^PDF^Base64^JVBERi0xLjQ....

A single ORU message can contain results for multiple orders by repeating the ORC/OBR/OBX group. Each OBR represents a separate order, and its child OBX segments carry that order’s results. The OBR sequence number (OBR-1) distinguishes between orders within the same message.