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HL7 204 - The HL7 Scheduling messages, SIU and SRM

Mark Olschesky

Chief Data Officer

May 4, 2016   HL7

The SIU (Schedule Information Unsolicited) and SRM (Schedule Request Message) messages contain information related to appointment scheduling. SRM messages are used for requesting changes to a health system’s schedule, such as a request for a new appointment booking, appointment rescheduling, modification, cancellation, etc. SIU messages are used to notify auxiliary applications of a change made to the health system’s schedule, such as a notification for the booking of a new appointment, appointment rescheduling, modification, cancellation, etc. Scheduling messages contain information about the appointment date and time, resources, services, location, and any other pertinent information regarding the appointment. The purpose or action prescribed by any scheduling message will depend entirely on the trigger event (See the List of Trigger Events below).

Following the standard HL7 message structure, an SIU or SRM message is made up of segments and groups of segments, each of which may be required, optional, repeatable, or some combination thereof. A quick note on reading HL7 message examples which seem to contain a bunch of [],{} etc. The general rule is as follows:

  • No brackets around it - Required
  • [] - Optional
  • { } - Repeating
  • [{ }] - Optional Repeating

Below are the message structures of both the SIU and the SRM:

SIU Message Structure

``` SIU Schedule Information Unsolicited

MSH Message Header SCH Schedule Activity Information [{NTE}] Notes and Comments (for Schedule Activity) PID Patient Identification [PD1] Patient Additional Demographics [ROL] Role (for Patient) [PV1] Patient Visit Information [PV2] Patient Visit Info Continued [{OBX}] Notes and Comments (for Patient) [{DG1}] Diagnosis (for Patient) { RGS Resource Group Segment { AIS Appointment Info. - Service [{NTE}] Notes and Comments (for Service) } [{ AIG Appointment Info. - General Resource [{NTE}] Notes and Comments (for Resource) }] [{ AIP Appointment Info. - Personnel [{NTE}] Notes and Comments (for Personnel) }] } ```

The SRM Message Structure

``` SRM Schedule Request Message

MSH Message Header ARQ Appointment Request Information [{NTE}] Notes and Comments (for Schedule Activity) PID Patient Identification [PD1] Patient Additional Demographics [ROL] Role (for Patient) [PV1] Patient Visit Information [PV2] Patient Visit Info Continued [{OBX}] Notes and Comments (for Patient) [{DG1}] Diagnosis (for Patient) { RGS Resource Group Segment { AIS Appointment Info. - Service [{NTE}] Notes and Comments (for Service) } [{ AIG Appointment Info. - General Resource [{NTE}] Notes and Comments (for Resource) }] [{ AIP Appointment Info. - Personnel [{NTE}] Notes and Comments (for Personnel) }] } ```

There are a few things to note about the message structures. As you may have already noticed, the structure of the two message types are virtually identical. We’ll discuss that more later. For now, we will explore the shared features of both the SIU and SRM:

  • The Resource Group segment (RGS) is always required, and may contain more than one resource group. This segment acts as a header for the collection of resource segments that follow it.

  • Within a Resource Group, the Appointment Service Information (AIS) is the only required resource segment. This suggests that any new/requested appointment must have a scheduled service attached to it.

  • Note the presence of multiple (optional, repeatable) Diagnosis (DG1) segments. If repeated, the first will be the primary diagnosis.

  • Note the presence of the OBX (Observation) segment as an optional, repeatable segment. The use here is different from its use in the ORU (Observational Report - Unsolicited) message. When used, it contains notes and comments pertaining to the patient in much the same way an NTE segment would, rather than information about observations and results. For instance, the OBX segments may contain a Transcribed Report (TX) with patient information that may be relevant to the appointment.

As mentioned before, the only apparent difference between the structure of an SIU message and an SRM message is the second segment. The SIU message contains an SCH segment whereas the SRM message contains an ARQ segment. Even these two segments share most of the same fields. However, there are some key differences, notably:

  • Date/Time Range In the SIU message, the SCH segment contains one field with all of the appointment timing/quantity information in one place (SCH.11). In the SRM message, the ARQ segment has four separate fields for appointment timing quantity. They consist of one required field for the requested start date/time range (ARQ.11) and the optional fields for appointment priority (ARQ.12), repeating interval (ARQ.13), and the interval duration (ARQ.14).

  • Audit Trail Contacts The SIU message can contain the name, phone number, address, and location information for the person who “placed” the appointment (SCH.12 - SCH.15), the person who “filled” the appointment (SCH.16 - SCH.19), and the person who “entered” the appointment (SCH.20 - SCH.22). As an SRM message is sent only when an appointment has not yet been filled, the ARQ segment only contains fields for the placer (ARQ.15 - ARQ.18) and enterer (ARQ.19 - ARQ.21) of the appointment.

  • Filler Status Code The status of the appointment is only present in SIU messages (SCH.25). This is, again, due to the fact that a scheduling request must be filled before it can have any status other than “requested”.

Apart from the few differences between the SCH segment and the ARQ segment, there is no structural difference between an SIU message and an SRM message. However, the main difference between any two message types comes not from the structure of the message, but from the action prescribed by the different trigger events.

List of Trigger Events

Trigger events for SRM:

Segment ID Description
S01 Request New Appointment Booking
S02 Request Appointment Rescheduling
S03 Request Appointment Modification
S04 Request Appointment Cancellation

Trigger Events for SIU:

Segment ID Description
S12 Notification of New Appointment Booking
S13 Notification of Appointment Rescheduling
S14 Notification of Appointment Modification
S15 Notification of Appointment Cancellation
S26 Notification that Patient did not show up for Scheduled Appointment

Message Construction

The message I want to send is: A female, Caucasian patient, Jane Fredericks, MRN:30745109, SSN:321-87-6543 born on May 1, 1973 and account number of 11396810 wants to schedule a new appointment to have an X-Ray taken of her ankle. The appointment request is being placed by Dr. James Matthews. The exact service to be performed is X-RAY ANKLE 3+ VW with the associated CPT code of 73610. This is based upon a diagnosis of Broken Ankle. Additional information that will need to be sent will include the appointment date and time, duration, sending and receiving systems, the version of HL7 being used etc. The request is approved and the hospital sends a notification for the new appointment booking.

Based on this information, the segments would be created as follows:

MSH - Message Header

Assuming an all Epic environment i.e. sending and receiving systems are all Epic and request is created at 2016/05/02 at 16:20:33. Version of HL7 being used is v2.3. Since this message is a notification for a new appointment booking, the message type is SIU and the trigger event is S12. This would result in a segment that looks like this.



This contains all of the scheduling information - the placer and filler application’s appointment identifiers, duration, start time, the person who requested the appointment, and the appointment status. To keep things simple, we’ll only include the identifiers and required information.


PID - Patient Identification

Since this message is a patient specific request, it needs all the associated patient info to prevent any confusion. This would include the patient’s identifier, full name, DOB, sex, race, address, phone number(s), account number, SSN and place of birth.

PID|1||30745109^^^^EPI||FREDERICKS^JANE^I^^MRS.^||19730501|F||Cauc|421 N. BAKER ST^^MADISON^WI^53513^US^^^DN|DN|(608)555-6789|(608)555-4321||S||11396810|321-87-6543||||^^^WI^^

PV1 - Patient Visit

This usually contains information on the admission information, attending, referring and consulting, admitting physician IDs and names and so on. I’ll just keep it simple and just have the attending physician’s info in the sample giving us

PV1|||^^^CARE HEALTH SYSTEMS^^^^^||| |1173^MATTHEWS^JAMES^A^^^||||||||||||610613||||||||||||||||||||||||||||||||V

DG1 - Diagnosis

Some basic context needs to be provided so that the billing systems can do their work so diagnosis information is also provided. So in ICD10 (I10), ankle fracture is coded as S82.


RGS - Resource Group

This is brief header for the group of resource segments that follow it. Included is the number of the resource group, the action prescribed (here it’s “add”, or ‘A’), and the group ID. This group ID may be used for modifying or rescheduling the resource group at a later date.


AIS - Appointment Info. - Service

This contains information related to the scheduled service. In this case, it will be an X-Ray for the patient’s ankle. Along with the CPT code for the scheduled service, the segment also contains the time the service is expected to start (may be different from the appointment start time) and the length of time the service will be needed.

AIS|1||73610^X-RAY ANKLE 3+ VW^CPT|20160515134500|15|min|45|min||

AIP - Appointment Info. - Personnel

This optional repeating segment identifies personnel needed for the appointment that are not explicitly mentioned anywhere else in the message. For the scheduled appointment, a radiologist (Allan Good) will be needed to perform the X-Ray. Just like the AIS segment, this segment contains the time the radiologist will be needed and for how long, which gives us


Putting it all together

To assemble the SIU message, we string together the message segments following the message structure outlined above:

MSH|^~\&|EPIC|EPIC|||20160502162033||SIU^S12|538|D|2.3|| SCH|01928374|57483920|||||||1|hr|1^^^20160515133000|||||||||1173^MATTHEWS^JAMES^A|||||BOOKED PID|1||30745109^^^^EPI||FREDERICKS^JANE^I^^MRS.^||19730501|F||Cauc|421 N. BAKER ST^^MADISON^WI^53513^US^^^DN|DN|(608)555-6789|(608)555-4321||S||11396810|321-87-6543||||^^^WI^^ PV1|||^^^CARE HEALTH SYSTEMS^^^^^||||1173^MATTHEWS^JAMES^A^^^||||||||||||610613||||||||||||||||||||||||||||||||V DG1||I10|S82^ANKLE FRACTURE^I10|ANKLE FRACTURE|| RGS|1|A|094 AIS|1||73610^X-RAY ANKLE 3+ VW^CPT|20160515134500|15|min|45|min|| AIP|1||1069^GOOD^ALLAN^B|RADIOLOGIST||20160515134500|15|min|45|min||

If you’re looking to integrate EHR data with your application without becoming an HL7 expert, Datica can help. Learn more about Datica Managed Integration Services for HL7 here.

Looking for further help on integrating an SIU or SRM feed with an EHR? Check out this post: SIU Integration Help

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