Message type

Laboratory order for multiple orders related to a single specimen

Submits a laboratory order where multiple test orders relate to a single specimen. The SPM segment defines the specimen and multiple ORC/OBR pairs define the orders. Laboratory systems use this to batch-process tests from one collection.

73segments

20required

8groups

v2.9HL7 version

# Zato
from zato.hl7v2 import HL7Message

# An incoming message ..
raw = 'MSH|^~\&|SENDER|FAC|RCV|DEST|20260701||' \
      'OML^O33^OML_O33|MSG001|P|2.9\r' \
      'ORC|NW|ORD001||GRP001|||1^BID\r' \
      'OBR|1||ORD001'

# .. parsed into a Python object ..
msg = HL7Message.parse(raw)

# .. whose fields we can now access.
order_control = msg.orc.order_control
order_number = msg.orc.placer_order_number
order_id = msg.obr.placer_order_number
test = msg.obr.universal_service_identifier

Python examples

Build and parse OML^O33 messages in Python

How to construct, send, receive, and extract fields from real-world OML^O33 messages.

Parse an incoming OML^O33 message

Demonstrates receiving and extracting key fields from a laboratory order for multiple orders related to a single specimen transaction

# Zato
from zato.hl7v2 import HL7Message

# An incoming message ..
raw = 'MSH|^~\&|SENDER|FAC|RCV|DEST|20260701||' \
      'OML^O33^OML_O33|MSG001|P|2.9\r' \
      'ORC|NW|ORD001||GRP001|||1^BID\r' \
      'OBR|1||ORD001'

# .. parsed into a Python object ..
msg = HL7Message.parse(raw)

# .. whose fields we can now access.
order_control = msg.orc.order_control
order_number = msg.orc.placer_order_number
order_id = msg.obr.placer_order_number
test = msg.obr.universal_service_identifier

Tutorials

Learn by building

Step-by-step guides for working with HL7 v2 in Zato.

MLLP

Receive and parse HL7 v2 messages

Set up an MLLP channel, parse incoming messages, and respond with acknowledgments.

Start tutorial Build

Build and send HL7 v2 messages

Construct HL7 v2 messages from scratch using typed segment classes and send them over MLLP.

Start tutorial

FAQ

Frequently asked questions

Use the HL7v2 message parser to extract the typed structure. The parsed message gives you direct access to every segment and field by name.

from zato.hl7v2 import HL7Message

raw = 'MSH|^~\&|SENDER|FACILITY|RECEIVER|DEST|20260401120000||OML^O33^OML_O33|MSG00001|P|2.9'
msg = HL7Message.parse(raw)

order_control = msg.orc.order_control
order_number = msg.orc.placer_order_number

Beyond the mandatory MSH header, the required segments are: PID, NK1, PV1, IN1, SPM, OBX, SAC, ORC. Optional segments provide additional detail when available.

Zato connects to any system that speaks HL7v2 over MLLP or FHIR over REST. This includes Epic, Cerner, Meditech, Allscripts, and other EHR platforms.

Yes, Zato has built-in MLLP support for sending and receiving HL7v2 messages. MLLP channels handle the framing protocol automatically.

Zato supports HL7 v2.9, which is backward compatible with earlier versions including v2.3, v2.5, and v2.7. Standard segments and datatypes are available as typed Python classes.

Yes. Zato handles both HL7v2 and FHIR natively, so you can parse v2 messages and build FHIR resources with IG-specific extensions in the same service. Typed Python classes are available for both protocols, including extensions from US Core, UK Core, Da Vinci, and other Implementation Guides.

Reference

OML^O33 segment composition

Segments that make up the OML^O33 message, in order. Groups are shown with their child segments.

#	Segment	Usage	Repeats	Description	Group
1	`MSH`	Required	No	Message header	-
2	`ARV`	Optional	Yes	Access restriction	-
3	`SFT`	Optional	Yes	Software segment	-
4	`UAC`	Optional	No	User authentication credential	-
5	`NTE`	Optional	Yes	Notes and comments	-
6	`PID`	Required	No	Patient identification	PATIENT
7	`PD1`	Optional	No	Patient additional demographic	PATIENT
8	`PRT`	Optional	Yes	Participation information	PATIENT
9	`OH1`	Optional	Yes	Employment status	PATIENT
10	`OH2`	Optional	Yes	Past or present job	PATIENT
11	`OH3`	Optional	No	Usual work	PATIENT
12	`OH4`	Optional	Yes	Combat zone work	PATIENT
13	`NTE`	Optional	Yes	Notes and comments	PATIENT
14	`NK1`	Required	No	Next of kin / associated parties	PATIENT
15	`OH2`	Optional	Yes	Past or present job	PATIENT
16	`OH3`	Optional	No	Usual work	PATIENT
17	`ARV`	Optional	Yes	Access restriction	PATIENT
18	`PV1`	Required	No	Patient visit	PATIENT
19	`PV2`	Optional	No	Patient visit - additional info	PATIENT
20	`PRT`	Optional	Yes	Participation information	PATIENT
21	`IN1`	Required	No	Insurance	PATIENT
22	`IN2`	Optional	No	Insurance additional info	PATIENT
23	`IN3`	Optional	No	Insurance additional info - certification	PATIENT
24	`GT1`	Optional	No	Guarantor	PATIENT
25	`AL1`	Optional	Yes	Patient allergy information	PATIENT
26	`SPM`	Required	No	Specimen	SPECIMEN
27	`NTE`	Optional	Yes	Notes and comments	SPECIMEN
28	`OBX`	Required	No	Observation result	SPECIMEN
29	`PRT`	Optional	Yes	Participation information	SPECIMEN
30	`SAC`	Required	No	Specimen container detail	SPECIMEN
31	`NTE`	Optional	Yes	Notes and comments	SPECIMEN
32	`ORC`	Required	No	Common order	SPECIMEN
33	`NTE`	Optional	Yes	Notes and comments	SPECIMEN
34	`PRT`	Optional	Yes	Participation information	SPECIMEN
35	`TQ1`	Required	No	Timing / quantity	TIMING
36	`TQ2`	Optional	Yes	Timing / quantity relationship	TIMING
37	`OBR`	Required	No	Observation request	OBSERVATION_REQUEST
38	`TCD`	Optional	No	Test code detail	OBSERVATION_REQUEST
39	`NTE`	Optional	Yes	Notes and comments	OBSERVATION_REQUEST
40	`PRT`	Optional	Yes	Participation information	OBSERVATION_REQUEST
41	`DG1`	Optional	Yes	Diagnosis	OBSERVATION_REQUEST
42	`REL`	Optional	No	Clinical relationship segment	OBSERVATION_REQUEST
43	`OBX`	Required	No	Observation result	OBSERVATION_REQUEST
44	`PRT`	Optional	Yes	Participation information	OBSERVATION_REQUEST
45	`TCD`	Optional	No	Test code detail	OBSERVATION_REQUEST
46	`NTE`	Optional	Yes	Notes and comments	OBSERVATION_REQUEST
47	`IPC`	Optional	No	Imaging procedure control segment	OBSERVATION_REQUEST
48	`SGH`	Optional	No	Segment group header	OBSERVATION_REQUEST
49	`PID`	Required	No	Patient identification	PATIENT_PRIOR
50	`PD1`	Optional	No	Patient additional demographic	PATIENT_PRIOR
51	`PRT`	Optional	Yes	Participation information	PATIENT_PRIOR
52	`ARV`	Optional	Yes	Access restriction	PATIENT_PRIOR
53	`PV1`	Required	No	Patient visit	PATIENT_VISIT_PRIOR
54	`PV2`	Optional	No	Patient visit - additional info	PATIENT_VISIT_PRIOR
55	`PRT`	Optional	Yes	Participation information	PATIENT_VISIT_PRIOR
56	`AL1`	Optional	Yes	Patient allergy information	OBSERVATION_REQUEST
57	`ORC`	Required	No	Common order	ORDER_PRIOR
58	`PRT`	Optional	Yes	Participation information	ORDER_PRIOR
59	`OBR`	Required	No	Observation request	ORDER_PRIOR
60	`NTE`	Optional	Yes	Notes and comments	ORDER_PRIOR
61	`PRT`	Required	No	Participation information	ORDER_PRIOR
62	`DEV`	Optional	Yes	Device	ORDER_PRIOR
63	`TQ1`	Required	No	Timing / quantity	ORDER_PRIOR
64	`TQ2`	Optional	Yes	Timing / quantity relationship	ORDER_PRIOR
65	`OBX`	Required	No	Observation result	ORDER_PRIOR
66	`PRT`	Optional	Yes	Participation information	ORDER_PRIOR
67	`NTE`	Optional	Yes	Notes and comments	ORDER_PRIOR
68	`SGT`	Optional	No	Segment group trailer	OBSERVATION_REQUEST
69	`FT1`	Optional	Yes	Financial transaction	SPECIMEN
70	`CTI`	Optional	Yes	Clinical trial identification	SPECIMEN
71	`BLG`	Optional	No	Billing	SPECIMEN
72	`DEV`	Required	No	Device	DEVICE
73	`OBX`	Optional	Yes	Observation result	DEVICE

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