HL7 OML_O33 Lab Orders for One Specimen

Several lab orders ride under the same specimen context.
HL7 message structure OML_O33 groups and segments from HL7 v2.5.1 Hide structure

These are the generated groups and segments for the version selected at the top of the page. The article explains the workflow, and this panel follows the chosen HL7 version.

Message Structure

SegmentNameRequiredRepeatable
MSH
 Message Header Yes No
SFT
 Software Segment No Yes
NTE
 Notes and Comments No Yes
OML_O33.PATIENT
 Patient group No No
PID
 Patient Identification Yes No
PD1
 Patient Additional Demographic No No
NTE
 Notes and Comments No Yes
NK1
 Next of Kin / Associated Parties No Yes
OML_O33.PATIENT_VISIT
 Patient Visit group No No
PV1
 Patient Visit Yes No
PV2
 Patient Visit - Additional Information No No
OML_O33.INSURANCE
 Insurance group No Yes
IN1
 Insurance Yes No
IN2
 Insurance Additional Information No No
IN3
 Insurance Additional Information, Certification No No
GT1
 Guarantor No No
AL1
 Patient Allergy Information No Yes
OML_O33.SPECIMEN
 Specimen group Yes Yes
SPM
 Specimen Yes No
OBX
 Observation/Result No Yes
SAC
 Specimen Container detail No Yes
OML_O33.ORDER
 Order group Yes Yes
ORC
 Common Order Yes No
OML_O33.TIMING
 Timing group No Yes
TQ1
 Timing/Quantity Yes No
TQ2
 Timing/Quantity Relationship No Yes
OML_O33.OBSERVATION_REQUEST
 Observation Request group No No
OBR
 Observation Request Yes No
TCD
 Test Code Detail No No
NTE
 Notes and Comments No Yes
DG1
 Diagnosis No Yes
OML_O33.OBSERVATION
 Observation group No Yes
OBX
 Observation/Result Yes No
TCD
 Test Code Detail No No
NTE
 Notes and Comments No Yes
OML_O33.PRIOR_RESULT
 Prior Result group No Yes
OML_O33.PATIENT_PRIOR
 Patient Prior group No No
PID
 Patient Identification Yes No
PD1
 Patient Additional Demographic No No
OML_O33.PATIENT_VISIT_PRIOR
 Patient Visit Prior group No No
PV1
 Patient Visit Yes No
PV2
 Patient Visit - Additional Information No No
AL1
 Patient Allergy Information No Yes
OML_O33.ORDER_PRIOR
 Order Prior group Yes Yes
ORC
 Common Order No No
OBR
 Observation Request Yes No
NTE
 Notes and Comments No Yes
OML_O33.TIMING_PRIOR
 Timing Prior group No Yes
TQ1
 Timing/Quantity Yes No
TQ2
 Timing/Quantity Relationship No Yes
OML_O33.OBSERVATION_PRIOR
 Observation Prior group Yes Yes
OBX
 Observation/Result Yes No
NTE
 Notes and Comments No Yes
FT1
 Financial Transaction No Yes
CTI
 Clinical Trial Identification No Yes
BLG
 Billing No No

OML_O33 is a laboratory order message for cases where multiple orders are related to a single specimen. It is more specimen-centric than the older general order layouts, which makes it useful in lab automation and specimen/container-aware workflows.

The sender is usually an order placer, LIS, EHR, or integration engine. The receiver needs to create lab work while preserving the specimen identity and the order list under that specimen.

A small OML O33 example

MSH|^~\&|EHR|CITYHOSP|LAB|CITYLAB|20260718103000||OML^O33^OML_O33|OML330001|P|2.5.1 PID|1||123456^^^CITYHOSP^MR||Smith^Jane^Anne^^Ms^^L||19800314|F PV1|1|O|CLINIC^12^^CITYHOSP||||12345^Careful^Clara SPM|1|SPEC330001^EHR||BLD^Blood^HL70487|||||||P SAC|||TUBE330001^EHR||||||||||||SER^Serum tube^L ORC|NW|ORD330001^EHR|||||^^^20260718104500|||12345^Careful^Clara OBR|1|ORD330001^EHR||718-7^Hemoglobin^LN|||20260718104500 ORC|NW|ORD330002^EHR|||||^^^20260718104500|||12345^Careful^Clara OBR|2|ORD330002^EHR||6690-2^White blood cell count^LN|||20260718104500

What systems do with it

The receiver creates one specimen record and multiple order records beneath it. SPM carries specimen identity and type. SAC can carry container detail. Each order group starts with ORC and usually has an OBR request.

This layout helps when a single draw, swab, or sample supports several tests. It keeps specimen collection, container handling, and order details together instead of repeating specimen data in loosely related ORC/OBR pairs.

How to read the structure

After the optional patient group, the required specimen group repeats. Inside each specimen, SPM is required, OBX and SAC can add specimen observations or container detail, and the order group repeats for each requested test.

Use the generated panel to notice where the hierarchy changes: patient, specimen, order, observation request, observation, and prior result are different levels. Mapping all identifiers into one flat order table loses the point of the message.

Implementation traps

Do not let each OBR create its own duplicate specimen if the message clearly groups them under one SPM. That mistake produces multiple specimen records for one physical sample.

Also decide how container identifiers are used. A specimen may have multiple containers, and a container may matter for routing, aliquoting, automation, or cancellation.

Reference notes

HL7 describes OML_O33 as a specimen-centric laboratory order where multiple orders are associated with one specimen, with optional multiple containers. See HL7 Europe OML_O33.