HL7 OMG_O19 (General Clinical Order) | Integration Soup HL7 Reference Guide

HL7 OMG_O19 General Clinical Order

A more specific order message for clinical orders that still revolve around ORC and OBR.

HL7 message structure OMG_O19 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
OMG_O19.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
OMG_O19.PATIENT_VISIT	Patient Visit group	No	No
PV1	Patient Visit	Yes	No
PV2	Patient Visit - Additional Information	No	No
OMG_O19.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
OMG_O19.ORDER	Order group	Yes	Yes
ORC	Common Order	Yes	No
OMG_O19.TIMING	Timing group	No	Yes
TQ1	Timing/Quantity	Yes	No
TQ2	Timing/Quantity Relationship	No	Yes
OBR	Observation Request	Yes	No
NTE	Notes and Comments	No	Yes
CTD	Contact Data	No	No
DG1	Diagnosis	No	Yes
OMG_O19.OBSERVATION	Observation group	No	Yes
OBX	Observation/Result	Yes	No
NTE	Notes and Comments	No	Yes
OMG_O19.SPECIMEN	Specimen group	No	Yes
SPM	Specimen	Yes	No
OBX	Observation/Result	No	Yes
OMG_O19.CONTAINER	Container group	No	Yes
SAC	Specimen Container detail	Yes	No
OBX	Observation/Result	No	Yes
OMG_O19.PRIOR_RESULT	Prior Result group	No	Yes
OMG_O19.PATIENT_PRIOR	Patient Prior group	No	No
PID	Patient Identification	Yes	No
PD1	Patient Additional Demographic	No	No
OMG_O19.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
OMG_O19.ORDER_PRIOR	Order Prior group	Yes	Yes
ORC	Common Order	No	No
OBR	Observation Request	Yes	No
OMG_O19.TIMING_PRIOR	Timing Prior group	No	Yes
TQ1	Timing/Quantity	Yes	No
TQ2	Timing/Quantity Relationship	No	Yes
NTE	Notes and Comments	No	Yes
CTD	Contact Data	No	No
OMG_O19.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

OMG_O19 is a general clinical order message. It covers the same broad order-management world as ORM_O01, but uses a v2.5.1 structure that is explicitly built around clinical orders with ORC, OBR, timing, observations, specimen details, prior results, and billing context.

The sender is usually an EHR, CPOE system, integration engine, or specialist clinical system. The receiver is the filler application that will perform or manage the ordered service. The trigger is any meaningful change to the order: new, cancel, update, hold, discontinue, replace, or another order-control event.

A small OMG order example

MSH|^~\&|EHR|CITYHOSP|CARDIO|CITYHOSP|20260718100000||OMG^O19^OMG_O19|OMG190001|P|2.5.1 PID|1||123456^^^CITYHOSP^MR||Smith^Jane^Anne^^Ms^^L||19800314|F PV1|1|O|CARD^ROOM2^^CITYHOSP||||12345^Careful^Clara ORC|NW|ORD550001^EHR|||||^^^20260718103000|||12345^Careful^Clara TQ1|1||||||20260718103000 OBR|1|ORD550001^EHR||ECG12^12 lead ECG^L|||20260718103000|||||||||12345^Careful^Clara OBX|1|ST|REASON^Reason for order^L||Palpitations and dizziness

What systems do with it

The receiver uses ORC to decide what action is being requested and OBR to understand the service. TQ1 and TQ2 refine timing. OBX under the order usually carries supporting clinical information, not final results. If the service is specimen-driven, SPM and SAC can identify the specimen and container context.

Downstream systems normally create or update a work item, then answer with ORG_O20 or a normal application acknowledgment depending on the interface agreement. The order is not truly under control until both sides agree what ORC-1 values they support.

How to read the structure

The patient group is optional in the base structure, but most patient-specific orders need PID and often PV1. The required order group starts at ORC, then carries timing and OBR detail. Optional DG1, OBX, SPM, FT1, CTI, and BLG groups add diagnosis, supporting observations, specimens, finance, trial, and billing details.

The prior-result group is easy to overlook. It lets the sender include previous demographics or result information that is relevant to the current order. That is useful, but only when the receiver knows not to file those OBX values as new results.

Implementation traps

The most common trap is treating every OMG as a new order. ORC-1 is the action. If the receiver ignores cancellation, hold, discontinue, replacement, and status values, the interface will create duplicate or stale work.

Also keep ORC and OBR identifiers aligned. The placer order number, filler order number, and placer group number are what let updates hit the existing order instead of creating a second one.

Reference notes

HL7's refactored OMG_O19 page describes the message as a general clinical order used for changes such as new orders, cancellations, and updates, with OBR as the order detail segment. See HL7 Europe OMG_O19. The HL7AU ordering notes are also useful for ORC behavior and order identifiers: HL7AU observation ordering.