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.
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:
PID Patient Identification PID|1||MRN12345^^^MAIN_HOSP^MR||DOE^JOHN^ALEXANDER||19800115|M Field Name Value Note PID-3 Patient Identifier List MRN12345^^^MAIN_HOSP^MR PID-5 Patient Name DOE^JOHN^ALEXANDER
PV1 Patient Visit PV1|1|I|ICU^0101^01^MAIN_HOSP
ORC Common Order ORC|RE|ORD5678^EPIC|FIL9012^LAB_SYS||CM|||202603011430|||ATT1234^SMITH^JANE^^^MD Field Name Value Note ORC-1 Order Control REResults ORC-2 Placer Order Number ORD5678^EPICOriginal order from CPOE ORC-3 Filler Order Number FIL9012^LAB_SYSLab accession number ORC-5 Order Status CMComplete
OBR Observation Request OBR|1|ORD5678^EPIC|FIL9012^LAB_SYS|24323-8^CMP^LN|||202603011445|||||||||ATT1234^SMITH^JANE^^^MD||||||202603011615||LAB|F Field Name Value Note OBR-4 Universal Service ID 24323-8^CMP^LNComprehensive Metabolic Panel (LOINC) OBR-7 Observation Date/Time 202603011445Specimen collected at 2:45 PM OBR-22 Results Report Date 202603011615Results finalized at 4:15 PM OBR-25 Result Status FFinal
OBX Observation/Result (Glucose) OBX|1|NM|2345-7^Glucose^LN||98|mg/dL|70-100|N|||F|||202603011600 Field Name Value Note OBX-2 Value Type NMNumeric OBX-3 Observation ID 2345-7^Glucose^LNLOINC code OBX-5 Observation Value 98 OBX-6 Units mg/dL OBX-7 Reference Range 70-100 OBX-8 Abnormal Flags NNormal OBX-11 Result Status FFinal
OBX Observation/Result (Creatinine) OBX|2|NM|2160-0^Creatinine^LN||1.1|mg/dL|0.6-1.2|N|||F|||202603011600
OBX Observation/Result (BUN) OBX|3|NM|3094-0^BUN^LN||18|mg/dL|7-20|N|||F|||202603011600
OBX Observation/Result (Sodium) OBX|4|NM|2951-2^Sodium^LN||140|mEq/L|136-145|N|||F|||202603011600
OBX Observation/Result (Potassium) OBX|5|NM|2823-3^Potassium^LN||4.2|mEq/L|3.5-5.0|N|||F|||202603011600
OBX Observation/Result (Chloride) OBX|6|NM|2075-0^Chloride^LN||102|mEq/L|98-106|N|||F|||202603011600
OBX Observation/Result (CO2) OBX|7|NM|2028-9^CO2^LN||24|mEq/L|22-29|N|||F|||202603011600
NTE Notes and Comments NTE|1||All values within normal limits. No critical results. Field Name Value Note NTE-3 Comment All values within normal limits. No critical results.
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:
Match the corrected result to the original using the filler order number (OBR-3)
Update the displayed value
Maintain an audit trail showing both original and corrected values
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.
HL7 ORM Messages Order Messaging — ORM^O01 structure, ORC order control codes, and bidirectional order/result workflows.
HL7 Integration Services HL7 v2 result integration — ORU interfaces, result routing, and clinical notification workflows.
HL7 Workbench Parse and validate ORU messages online with OBX value inspection and segment highlighting.