HL7 v2 trigger events

A trigger event is the real event that causes a system to send a message.

What a trigger event is

Here is a short admission message. The second part of MSH-9 is A01, the trigger event. A01 means a patient was admitted. The same code is in EVN-1.

MSH|^~\&|EPIC|STJOSEPH|LABSYS|STJOSEPH|20240314093015||ADT^A01^ADT_A01|MSG00017|P|2.5.1
EVN|A01|20240314093000
PID|1||1000345678^^^STJOSEPH^MR||CARTWRIGHT^ELEANOR^MAY^^^^L||19510822|F
PV1|1|I|3W^312^A^STJOSEPH

The receiver reads A01 and opens a new visit.

The trigger event is not the same as the message structure. One structure often serves several events. ADT_A01 carries A01, A04, A08 and A13. The structure says how to parse the message. The event says why it was sent.

Common trigger events

The standard defines 266 trigger events. Each one links to the message type that sends it. These are some of the common trigger events:

A01Admit/Visit Notification
A patient has been admitted and given a bed. This is the event that starts an inpatient stay, and it is the one most systems treat as "this person is now here".
A03Discharge/End Visit
The patient has left. The visit is over, and the message usually carries the discharge time and disposition.
A04Register a Patient
A patient has been registered for a visit without being admitted to a bed: an outpatient clinic, an emergency attendance, a day case.
A08Update Patient Information
Something already sent has changed: a corrected name, a new address, an updated insurer. The receiver is expected to overwrite what it holds.
R01Unsolicited Observation Message
Results are being sent without anyone having asked for them at that moment: a lab releasing a panel, a device reporting a reading. The producing system pushes; the receiver did not query.
O01general order message
An order is being placed, changed or cancelled. Which of those it is comes from the order control code in ORC-1, not from the trigger event.
S12Notification of new appointment booking
A new appointment has been booked.

All trigger events

Here's a list of all 266 trigger events, along with the message type that sends each one, its structure and its chapter.

Event	Name	Meaning	Sent by	Structure	Chapter
A01	Admit/Visit Notification	A patient has been admitted and given a bed. This is the event that starts an inpatient stay, and it is the one most systems treat as "this person is now here".	ADT	`ADT_A01`	03
A02	Transfer a Patient	The patient has moved to a different bed, room or ward while remaining admitted. The stay continues; only the location changed.	ADT	`ADT_A02`	03
A03	Discharge/End Visit	The patient has left. The visit is over, and the message usually carries the discharge time and disposition.	ADT	`ADT_A03`	03
A04	Register a Patient	A patient has been registered for a visit without being admitted to a bed: an outpatient clinic, an emergency attendance, a day case.	ADT	`ADT_A01`	03
A05	Pre-Admit a Patient	A visit has been booked in advance and the patient has not arrived yet. Systems that need the record to exist before the patient turns up rely on this.	ADT	`ADT_A05`	03
A06	Change an Outpatient to an Inpatient		ADT	`ADT_A06`	03
A07	Change an Inpatient to an Outpatient		ADT	`ADT_A06`	03
A08	Update Patient Information	Something already sent has changed: a corrected name, a new address, an updated insurer. The receiver is expected to overwrite what it holds.	ADT	`ADT_A01`	03
A09	Patient Departing - Tracking		ADT	`ADT_A09`	03
A10	Patient Arriving - Tracking		ADT	`ADT_A09`	03
A11	Cancel Admit / Visit Notification	An admission that was sent in error is being taken back. The receiver should undo the admission rather than record a discharge.	ADT	`ADT_A09`	03
A12	Cancel Transfer	A transfer sent in error is being taken back, returning the patient to their previous location.	ADT	`ADT_A12`	03
A13	Cancel Discharge / End Visit	A discharge sent in error is being taken back. The patient is still here and the visit is open again.	ADT	`ADT_A01`	03
A14	Pending Admit		ADT	`ADT_A05`	03
A15	Pending Transfer		ADT	`ADT_A15`	03
A16	Pending Discharge		ADT	`ADT_A16`	03
A17	Swap Patients		ADT	`ADT_A17`	03
A18	Merge Patient Information		ADT	`ADT_A18`	03
A19	Patient Query		ADR, QRY	`ADR_A19` +1	03
A20	Bed Status Update		ADT	`ADT_A20`	03
A21	Patient Goes on a Leave of Absence		ADT	`ADT_A21`	03
A22	Patient Returns From a Leave of Absence		ADT	`ADT_A21`	03
A23	Delete a Patient Record		ADT	`ADT_A21`	03
A24	Link Patient Information		ADT	`ADT_A24`	03
A25	Cancel Pending Discharge		ADT	`ADT_A21`	03
A26	Cancel Pending Transfer		ADT	`ADT_A21`	03
A27	Cancel Pending Admit		ADT	`ADT_A21`	03
A28	Add Person or Patient Information	A new person record has been created, independently of any visit. Used to keep a shared patient index in step.	ADT	`ADT_A05`	03
A29	Delete Person Information		ADT	`ADT_A21`	03
A30	Merge Person Information		ADT	`ADT_A30`	03
A31	Update Person Information	Demographic details on the person record have changed, with no particular visit in view.	ADT	`ADT_A05`	03
A32	Cancel Patient Arriving - Tracking		ADT	`ADT_A21`	03
A33	Cancel Patient Departing - Tracking		ADT	`ADT_A21`	03
A34	Merge Patient Information - Patient ID Only		ADT	`ADT_A30`	03
A35	Merge Patient Information - Account Number Only		ADT	`ADT_A30`	03
A36	Merge patient information - patient ID and account number (for backward compatibility only)		ADT	`ADT_A30`	03
A37	Unlink Patient Information		ADT	`ADT_A37`	03
A38	Cancel Pre-Admit		ADT	`ADT_A38`	03
A39	Merge Person - Patient ID		ADT	`ADT_A39`	03
A40	Merge Patient - Patient Identifier List	Two records turned out to be the same person and have been merged. The message names both the surviving identifier and the one being retired, and receivers must repoint anything they hold against the old one.	ADT	`ADT_A39`	03
A41	Merge Account - Patient Account Number		ADT	`ADT_A39`	03
A42	Merge Visit - Visit Number		ADT	`ADT_A39`	03
A43	Move Patient Information - Patient Identifier List		ADT	`ADT_A43`	03
A44	Move Account Information - Patient Account Number	A visit was filed against the wrong patient and is being moved to the right one.	ADT	`ADT_A43`	03
A45	Move Visit Information - Visit Number		ADT	`ADT_A45`	03
A46	Change Patient ID		ADT	`ADT_A30`	03
A47	Change Patient Identifier List		ADT	`ADT_A30`	03
A48	Change Alternate Patient ID		ADT	`ADT_A30`	03
A49	Change Patient Account Number		ADT	`ADT_A30`	03
A50	Change Visit Number		ADT	`ADT_A50`	03
A51	Change Alternate Visit ID		ADT	`ADT_A50`	03
A52	Cancel Leave of Absence for a Patient		ADT	`ADT_A52`	03
A53	Cancel Patient Returns from a Leave of Absence		ADT	`ADT_A52`	03
A54	Change Attending Doctor		ADT	`ADT_A54`	03
A55	Cancel Change Attending Doctor		ADT	`ADT_A52`	03
A60	Update Adverse Reaction Information		ADT	`ADT_A60`	03
A61	Change Consulting Doctor		ADT	`ADT_A61`	03
A62	Cancel Change Consulting Doctor		ADT	`ADT_A61`	03
B01	Add Personnel Record		PMU	`PMU_B01`	15
B02	Update Personnel Record		PMU	`PMU_B01`	15
B03	Delete Personnel Record		PMU	`PMU_B03`	15
B04	Activate Practicing Person		PMU	`PMU_B04`	15
B05	Deactivate Practicing Person		PMU	`PMU_B04`	15
B06	Terminate Practicing Person		PMU	`PMU_B04`	15
B07	Grant Certificate/Permission		PMU	`PMU_B07`	15
B08	Revoke Certificate/Permission		PMU	`PMU_B08`	15
C01	Register a patient on a clinical trial		CRM		07
C09	Automated time intervals for reporting, like monthly		CSU		07
I01	Request for Insurance Information		RPI, RQI	`RPI_I01` +1	11
I02	Request/Receipt of Patient Selection Display List		RPL, RQI	`RPL_I02` +1	11
I03	Request/Receipt of Patient Selection List		RPR, RQI	`RPR_I03` +1	11
I04	request for patient demographic data		RPI, RQP	`RPI_I04` +1	11
I05	Request For Patient Clinical Information		RCI, RQC	`RCI_I05` +1	11
I06	Request/Receipt of Clinical Data Listing		RCL, RQC	`RCL_I06` +1	11
I07	Unsolicited Insurance Information		RQI	`RQI_I01`	11
I08	Request for Treatment Authorization Information		RPA, RQA		11
I12	Patient Referral		REF, RRI		11
J01	cancel query/acknowledge message		QCN	`QCN_J01`	05
J02	cancel subscription/acknowledge message		QCN	`QCN_J01`	05
K11	Segment pattern response in response to QBP^Q11		RSP	`RSP_K11`	05
K13	Tabular response in response to QBP^Q13		RTB	`RTB_K13`	05
K15	Display response in response to QBP^Q15		RDY	`RDY_K15`	05
K21	Get person demographics response		RSP	`RSP_K21`	05
K22	Find candidates response		RSP	`RSP_K21`	05
K23	Get corresponding identifiers response		RSP	`RSP_K23`	05
K24	Allocate identifiers response		RSP	`RSP_K23`	05
K25	Personnel Information by Segment Response		RSP	`RSP_K25`	05
K31	RSP – Dispense History		RSP	`RSP_K31`	05
M01	Master File Notification		MFK, MFN, MFQ, MFR	`MFK_M01` +1	08
M02	Staff/Practitioner Master File Message		MFK, MFN	`MFK_M01` +1	08
M03	Master File Notification - Test/Observation		MFK, MFN	`MFK_M01` +1	08
M04	Charge Description Master File Message		MFK, MFN, MFR	`MFK_M01` +2	08
M05	Patient Location Master File Message		MFK, MFN, MFR	`MFK_M01` +2	08
M06	Clinical study with phases and schedules master file		MFK, MFN, MFR	`MFK_M01` +2	08
M07	Clinical study without phases but with schedules master file		MFK, MFN, MFR	`MFK_M01` +2	08
M08	Master File Notification - Test/Observation (Numeric)		MFK, MFN	`MFK_M01` +1	08
M09	Test/observation (categorical) master file		MFK, MFN	`MFK_M01` +1	08
M10	Master File Notification - Test/Observation Batteries		MFK, MFN	`MFK_M01` +1	08
M11	Master File Notification - Test/Calculated Observations		MFK, MFN	`MFK_M01` +1	08
M12	Master file notification message		MFK, MFN	`MFK_M01` +1	08
M13	Master File Notification - General		MFK, MFN	`MFK_M01` +1	08
M14	Master File Notification - Site Defined		MFK, MFN	`MFK_M01` +1	08
M15	Inventory Item Master File Message		MFK, MFN	`MFK_M01` +1	08
N01	Application Management Query Message		NMQ, NMR	`NMQ_N01` +1	14
N02	Application Management Data Message		NMD	`NMD_N02`	14
O01	general order message	An order is being placed, changed or cancelled. Which of those it is comes from the order control code in ORC-1, not from the trigger event.	ORM, RAS	`ORM_O01` +1	04
O02	general order response message response to any ORM	A response to an order, saying what the filling system did with it.	ORR	`ORR_O02`	04
O03	Dietary Order		OMD	`OMD_O03`	04
O04	dietary order acknowledgment		ORD	`ORD_O04`	04
O05	stock requisition order message		OMS	`OMS_O05`	04
O06	stock requisition order acknowledgment message		ORS	`ORS_O06`	04
O07	non-stock requisition order message		OMN	`OMN_O07`	04
O08	non-stock requisition order acknowledgment message		ORN	`ORN_O08`	04
O09	Pharmacy/Treatment Order Message		OMP	`OMP_O09`	04
O10	Pharmacy/Treatment Order Acknowledgment		ORP	`ORP_O10`	04
O11	Pharmacy/Treatment Encoded Order Message		RDE	`RDE_O11`	04
O12	Pharmacy/Treatment Encoded Order Acknowledgment		RRE	`RRE_O12`	04
O13	Pharmacy/Treatment Dispense Message		RDS	`RDS_O13`	04
O14	Pharmacy/Treatment Dispense Acknowledgement Message		RRD	`RRD_O14`	04
O15	Pharmacy/Treatment Give Message		RGV	`RGV_O15`	04
O16	Pharmacy/Treatment Give Acknowledgment Message		RRG	`RRG_O16`	04
O17	Pharmacy/Treatment Administration Message		RAS	`RAS_O17`	04
O18	Pharmacy/treatment administration acknowledgment		RRA	`RRA_O18`	04
O19	general clinical order message		OMG	`OMG_O19`	04
O20	general clinical order acknowledgement message		ORG	`ORG_O20`	04
O21	laboratory order message		OML	`OML_O21`	04
O22	general laboratory order response message to any OML		ORL	`ORL_O22`	07
O23	Imaging Order Message		OMI	`OMI_O23`	04
O24	Imaging Order Response Message To Any OMI		ORI	`ORI_O24`	04
O25	Pharmacy/Treatment Refill Authorization Request Message		RDE	`RDE_O11`	04
O26	Pharmacy/Treatment Refill Authorization Acknowledgement		RRE	`RRE_O12`	04
O27	Blood Product Order Message		OMB	`OMB_O27`	04
O28	Blood Product Order Acknowledgment		ORB	`ORB_O28`	04
O29	Blood Product Dispense Status Message		BPS	`BPS_O29`	04
O30	Blood Product Dispense Status Acknowledgment		BRP	`BRP_O30`	04
O31	Blood Product Transfusion/Disposition Message		BTS	`BTS_O31`	04
O32	Blood Product Transfusion/Disposition Acknowledgment		BRT	`BRT_O32`	04
O33	Laboratory order for multiple orders related to a single specimen		OML	`OML_O33`	04
O34	Laboratory order response message to a multiple order related to single specimen OML		ORL	`ORL_O34`	07
O35	Laboratory order for multiple orders related to a single container of a specimen		OML	`OML_O35`	04
O36	Laboratory order response message to a single container of a specimen OML		ORL	`ORL_O36`	07
P01	Add Patient Account		BAR	`BAR_P01`	06
P02	Purge Patient Accounts		BAR	`BAR_P02`	06
P03	Post Detail Financial Transactions	Charges are being posted against a patient account: a procedure performed, a supply used, an adjustment made.	DFT	`DFT_P03`	06
P05	Update Account		BAR	`BAR_P05`	06
P06	End Account		BAR	`BAR_P06`	06
P07	Unsolicited initial individual product experience report		PEX		07
P09	Summary Product Experience Report		SUR	`SUR_P09`	07
P10	BAR/ACK -Transmit Ambulatory Payment Classification(APC)		BAR	`BAR_P10`	06
P11	Post Detail Financial Transactions - Expanded		DFT	`DFT_P11`	06
P12	Update Diagnosis/Procedure		BAR	`BAR_P12`	06
PC1	PC/ problem add		PPR		12
PC4	Patient Care Problem Query		QRY	`QRY_PC4`	03
PC5	Patient Problem Response		PRR	`PRR_PC5`	12
PC6	PC/ goal add		PGL		12
PC9	Patient Goal Query		QRY	`QRY_PC4`	03
PCA	Patient Goal Response		PPV	`PPV_PCA`	12
PCB	PC/ pathway (problem-oriented) add		PPP		12
PCE	Patient Pathway (Problem-Oriented) Query		QRY	`QRY_PC4`	03
PCF	Patient Pathway (Problem-Oriented) Response		PTR	`PTR_PCF`	12
PCG	PC/ pathway (goal-oriented) add		PPG		12
PCK	Patient Pathway (Goal-Oriented) Query		QRY	`QRY_PC4`	03
PCL	Patient Pathway (Goal-Oriented) Response		PPT	`PPT_PCL`	12
Q01	original mode display query - immediate response		DSR, QRY		05
Q02	deferred query		QCK, QRY		05
Q03	deferred response to a query		DSR		05
Q04	embedded query language query		EQQ		05
Q05	unsolicited display update message		UDM		05
Q06	query response for order status		OSQ, OSR	`OSQ_Q06` +1	04
Q07	Virtual Table query		VQQ		05
Q08	stored procedure request		SPQ		05
Q09	event replay query		RQQ		05
Q11	Query by parameter requesting an RSP segment pattern response		QBP	`QBP_Q11`	05
Q13	Query by parameter requesting an RTB - tabular response		QBP	`QBP_Q13`	05
Q15	Query by parameter requesting an RDY display response		QBP	`QBP_Q15`	05
Q16	Create subscription		QSB	`QSB_Q16`	05
Q17	query for previous events		QVR	`QVR_Q17`	05
Q21	Get person demographics		QBP	`QBP_Q21`	05
Q22	Find candidates		QBP	`QBP_Q21`	05
Q23	Get corresponding identifiers		QBP	`QBP_Q21`	05
Q24	Allocate identifiers		QBP	`QBP_Q21`	05
Q25	Personnel Information by Segment Query		QBP	`QBP_Q21`	05
Q26	Pharmacy/Treatment Order Response		QRY	`QRY_Q01`	03
Q27	Pharmacy/Treatment Administration Information		QRY	`QRY_Q01`	03
Q28	Pharmacy/Treatment Dispense Information		QRY	`QRY_Q01`	03
Q29	Pharmacy/Treatment Encoded Order Information		QRY	`QRY_Q01`	03
Q30	Pharmacy/Treatment Dose Information		QRY	`QRY_Q01`	03
Q31	QBP – Dispense History		QBP	`QBP_Q11`	05
R01	Unsolicited Observation Message	Results are being sent without anyone having asked for them at that moment: a lab releasing a panel, a device reporting a reading. The producing system pushes; the receiver did not query.	ORU	`ORU_R01`	07
R02	Query for results of observation		QRY	`QRY_R02`	03
R04	Response to query; transmission of requested observation		ORF	`ORF_R04`	07
R07	Enhanced Display Response		EDR		05
R08	Tabular Data Response		TBR		05
R09	Event Replay Response		ERP		05
R11			RSP		05
R21	Unsolicited Laboratory Observation Message		OUL	`OUL_R21`	07
R22	Unsolicited Specimen Oriented Observation Message –		OUL	`OUL_R22`	07
R23	Unsolicited Specimen Container Oriented Observation Message		OUL	`OUL_R23`	07
R24	Unsolicited Order Oriented Observation Message –		OUL	`OUL_R24`	07
R30	Unsolicited Point-Of-Care Observation Message Without Existing Order - Place An Order		ORU	`ORU_R30`	07
R31	Unsolicited New Point-Of-Care Observation Message - Search For An Order		ORU	`ORU_R30`	07
R32	Unsolicited Pre-Ordered Point-Of-Care Observation		ORU	`ORU_R30`	07
RAR			RAR	`RAR_RAR`	04
RDR			RDR	`RDR_RDR`	04
RER			RER	`RER_RER`	04
RGR			RGR	`RGR_RGR`	04
ROR	Pharmacy prescription order query response		ROR	`ROR_ROR`	04
S01	Request new appointment booking		SRM, SRR		10
S12	Notification of new appointment booking	A new appointment has been booked.	SIU		10
S25	Schedule Query Message and Response		SQM, SQR	`SQM_S25` +1	10
T01	Original Document Notification		MDM	`MDM_T01`	09
T02	Original Document Notification and Content	A clinical document is available, and the document content travels with the message rather than being fetched separately.	MDM	`MDM_T02`	09
T03	Document Status Change Notification		MDM	`MDM_T01`	09
T04	Document status change notification and content		MDM	`MDM_T02`	09
T05	Document Addendum Notification		MDM	`MDM_T01`	09
T06	Document Addendum Notification and Content	A document already sent has been edited, and this carries the new content.	MDM	`MDM_T02`	09
T07	Document Edit Notification		MDM	`MDM_T01`	09
T08	Document Edit Notification and Content		MDM	`MDM_T02`	09
T09	Document Replacement Notification		MDM	`MDM_T01`	09
T10	Document Replacement Notification and Content		MDM	`MDM_T02`	09
T11	Document Cancel Notification		MDM	`MDM_T01`	09
T12	Document Query		DOC, QRY	`DOC_T12`	09
U01	Automated Equipment Status Update		ESU	`ESU_U01`	13
U02	Automated Equipment Status Request		ESR	`ESR_U02`	13
U03	Specimen Status Update		SSU	`SSU_U03`	13
U04	Specimen Status Request		SSR	`SSR_U04`	13
U05	Automated Equipment Inventory Update		INU	`INU_U05`	13
U06	Automated Equipment Inventory Request		INR	`INR_U06`	13
U07	Automated Equipment Command		EAC	`EAC_U07`	13
U08	Automated Equipment Response		EAR	`EAR_U08`	13
U09	Automated Equipment Notification		EAN	`EAN_U09`	13
U10	Automated equipment test code settings update		TCU	`TCU_U10`	13
U11	Automated equipment test code settings request		TCU	`TCU_U10`	13
U12	Automated Equipment Log/Service Update		LSU	`LSU_U12`	13
U13	Automated Equipment Log/Service Request		LSU	`LSU_U12`	13
V01	Query For Vaccination Record		VXQ	`VXQ_V01`	04
V02	Response to vaccination query returning multiple PID matches		VXX	`VXX_V02`	04
V03	Vaccination Record Response		VXR	`VXR_V03`	04
V04	Unsolicited Vaccination Record Update		VXU	`VXU_V04`	04
Z73			QBP	`QBP_Z73`	05
Z74			RTB	`RTB_Z74`	05
Z75			QBP	`QBP_Q13`	05
Z76			RTB	`RTB_K13`	05
Z77			QBP	`QBP_Q13`	05
Z78			RTB	`RTB_K13`	05
Z79			QBP	`QBP_Q15`	05
Z80			RSP	`RSP_K11`	05
Z81			QBP	`QBP_Q11`	05
Z82			RSP	`RSP_Z82`	05
Z83			QSB	`QSB_Q16`	05
Z84			RSP	`RSP_K11`	05
Z85			QBP	`QBP_Q11`	05
Z86			RSP	`RSP_Z86`	05
Z87			QBP	`QBP_Q11`	05
Z88			RSP	`RSP_Z88`	05
Z89			QBP	`QBP_Q11`	05
Z90			RSP	`RSP_Z90`	05
Z91			QBP	`QBP_Q13`	05
Z92			RTB	`RTB_K13`	05
Z93			QBP	`QBP_Q13`	05
Z94			RTB	`RTB_K13`	05
Z95			QBP	`QBP_Q13`	05
Z96			RTB	`RTB_K13`	05
Z97			QBP	`QBP_Q15`	05
Z98			RDY	`RDY_K15`	05
Z99			QBP	`QBP_Q13`	05