LINKMED® Interface Tutorial: HL7 ADT EVENT TYPES
5.4 Event A04-Register a Patient (ADT^A04)

An A04 event signals that the patient has arrived or checked in as a one-time, or recurring outpatient, and is not assigned to a bed. One example might be its use to signal the beginning of a visit to the Emergency Room (= Casualty, etc.). Note that some systems refer to these events as outpatient registrations or emergency admissions. PV1-44 - Admit Date/Time is used for the visit start date/time.
The Register message is as follows:

MSH..[{SFT}]..[UAC]..EVN..PID..[PD1]..[{ARV}]..[{ROL}]..[{NK1}]..PV1..[PV2]..[{ARV}]..[{ROL}]..[{DB1}]..
[{OBX}]..[{AL1}]..{{DG1}]..[DRG][{PR1}]..[{ROL}]..[{GT1}]..[{IN1}]..[IN2]..[{IN3}]..[{ROL}]..
[ACC]..[UB1]..[UB2]..[PDA]

5.5 Event A05-Pre-admit a Patient (ADT^A05)

An A05 event is sent when a patient undergoes the pre-admission process. During this process, episode-related data is collected in preparation for a patient's visit or stay in a healthcare facility. For example, a pre-admit may be performed prior to inpatient or outpatient surgery so that lab tests can be performed prior to the surgery. This event can also be used to pre-register a non-admitted patient.
The Pre-admit a Patient message is as follow:

MSH..[{SFT}]..[UAC]..EVN..PID..[PD1]..{{ARV}]..[{ROL}]..[{NK1}]..PV1..[PV2]..[{ARV}]..[{ROL}]..[{DB1}]..
[{OBX}][{AL1}]..[{DG1]}..[DRG]..[{PR1}]..[{ROL}]..[{GT1}]....[{IN1}]..[IN2]..[{IN3}]..[{ROL}]..[ACC]..[UB1]..[UB2]

5.6 Event A06-Change an Outpatient to Inpatient (ADT^A06)

An A06 event is sent when a patient who was present for a non-admitted visit is being admitted after an evaluation of the seriousness of the patient's condition. This event changes a patient's status from non-admitted to admitted. The new patient location should appear in PV1-3 - Assigned Patient Location, while the old patient location (if different) should appear in PV1-6 - Prior Patient Location. The new patient class should appear in PV1-2 - Patient Class.
The Change an Outpatient to Inpatient message is as follows:

MSH..[{SFT}]..[UAC]..EVN..PID..[PD1]..[{ARV}]..[{ROL}]..[MRG]..[{NK1}]..PV1..[PV2]..[{ARV}]..[{ROL}]..
[{DB1}]..[{OBX}]..[{AL1}]..[{DG1}]..[DRG]..[{PR1}]..[{ROL}]..[{GT1}]..[{IN1}]..[IN2]..[{IN3}]..[{ROL}]..
[ACC]..[UB1]..[UB2]

5.7 Event A07-Change an Inpatient to Outpatient (ADT^A07)

An A07 event is sent when a patient who was admitted changes his/her status to "no longer admitted" but is still being seen for this episode of care. This event changes a patient from an "admitted" to a "non-admitted" status. The new patient location should appear in PV1-3 - Assigned Patient Location, while the old patient location (if different) should appear in PV1-6 - Prior Patient Location.
The Inpatient to Outpatient message is as follows:

MSH..[{SFT}]..[UAC]..EVN..PID..[PD1]..[{ARV}]..[{ROL}]..[MRG]..[{NK1}]..PV1..[PV2]..[{ARV}]..[{ROL}]..
[{DB1}]..[{OBX}]..[{AL1}]..[{DG1}]..[DRG]..{{PR1}]..[{ROL}]..[{GT1}]..[{IN1}]..[IN2]..[{IN3}]..[{ROL}]..
[ACC]..[UB1]..[UB2]



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