HL7 OML_O35 (Lab Orders for One Container) | Integration Soup HL7 Reference Guide

HL7 OML_O35 Lab Orders for One Container

The specimen is known, the container is central, and the orders sit under it.

HL7 message structure OML_O35 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

Segment	Name	Required	Repeatable
MSH	Message Header	Yes	No
SFT	Software Segment	No	Yes
NTE	Notes and Comments	No	Yes
OML_O35.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_O35.PATIENT_VISIT	Patient Visit group	No	No
PV1	Patient Visit	Yes	No
PV2	Patient Visit - Additional Information	No	No
OML_O35.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_O35.SPECIMEN	Specimen group	Yes	Yes
SPM	Specimen	Yes	No
OBX	Observation/Result	No	Yes
OML_O35.SPECIMEN_CONTAINER	Specimen Container group	Yes	Yes
SAC	Specimen Container detail	Yes	No
OML_O35.ORDER	Order group	Yes	Yes
ORC	Common Order	Yes	No
OML_O35.TIMING	Timing group	No	Yes
TQ1	Timing/Quantity	Yes	No
TQ2	Timing/Quantity Relationship	No	Yes
OML_O35.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_O35.OBSERVATION	Observation group	No	Yes
OBX	Observation/Result	Yes	No
TCD	Test Code Detail	No	No
NTE	Notes and Comments	No	Yes
OML_O35.PRIOR_RESULT	Prior Result group	No	Yes
OML_O35.PATIENT_PRIOR	Patient Prior group	No	No
PID	Patient Identification	Yes	No
PD1	Patient Additional Demographic	No	No
OML_O35.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_O35.ORDER_PRIOR	Order Prior group	Yes	Yes
ORC	Common Order	No	No
OBR	Observation Request	Yes	No
NTE	Notes and Comments	No	Yes
OML_O35.TIMING_PRIOR	Timing Prior group	No	Yes
TQ1	Timing/Quantity	Yes	No
TQ2	Timing/Quantity Relationship	No	Yes
OML_O35.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_O35 is a laboratory order message for multiple orders related to a single container of a specimen. It is useful when the physical container is the organizing unit for the lab workflow, not just a detail attached somewhere below the order.

Compared with OML_O33, O35 pushes the hierarchy one step deeper: patient, specimen, specimen container, then orders. That distinction matters in automation, aliquoting, routing, and container-specific cancellation or rejection workflows.

A small OML O35 example

MSH|^~\&|EHR|CITYHOSP|LAB|CITYLAB|20260718104000||OML^O35^OML_O35|OML350001|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|SPEC350001^EHR||BLD^Blood^HL70487|||||||P SAC|||TUBE350001^EHR||||||||||||LAV^Lavender top tube^L ORC|NW|ORD350001^EHR|||||^^^20260718105000|||12345^Careful^Clara OBR|1|ORD350001^EHR||CBC^Complete blood count^L|||20260718105000 ORC|NW|ORD350002^EHR|||||^^^20260718105000|||12345^Careful^Clara OBR|2|ORD350002^EHR||RETIC^Reticulocyte count^L|||20260718105000

What systems do with it

The sender is saying: here is the specimen, here is a specific container, and here are the orders that belong to that container. The lab can use that hierarchy for accessioning, tracking, automation routing, and container-level status.

SPM identifies the specimen. SAC identifies the container. ORC and OBR describe each order under that container.

How to read the structure

The required specimen group contains a required specimen-container group, and that container group contains the repeating order groups. That is the core difference from OML_O33.

Optional OBX and TCD details can carry specimen/order observations or test-code detail. Use them deliberately; do not make the receiver guess whether an OBX is an order question, a specimen observation, or a prior result.

Implementation traps

The danger is ignoring the container level. If the receiver only reads the ORC/OBR pairs, it can lose the association between an order and the tube or container that should perform it.

Also be careful when one specimen has several containers. O35 is best when the container hierarchy is meaningful. If the order is simply specimen-centric with optional containers, O33 may be a cleaner fit.

Reference notes

HL7 describes OML_O35 as a laboratory order where one or more specimens have one to many containers and each container may have one to many orders. See HL7 Europe OML_O35.