HL7 ADT A55 Message: Cancel Change Attending Doctor, Structure, Segments & Examples

The HL7 A55 message is an Admit, Discharge, Transfer (ADT) event used to cancel a previously recorded change to a patient's attending doctor. Known as ADT A55: Cancel Change Attending Doctor, this event allows healthcare applications to correct attending physician assignments when an earlier A54 attending doctor change was entered incorrectly or withdrawn.

Attending doctor information supports clinical coordination, documentation, administrative responsibility, and encounter management. When an authorized system cancels a previous attending doctor change, connected applications must reconcile the correction without altering unrelated encounter information.

This guide explains A55 message structure, important fields, examples, Mirth Connect implementation, acknowledgment handling, and troubleshooting.

What Is an HL7 ADT A55 Message?

An HL7 ADT A55 message communicates the cancellation of a previously recorded attending doctor change. It belongs to the HL7 Version 2 patient administration message family and is associated with correcting an earlier A54 event.

The receiving application uses A55 to identify the affected patient encounter and reverse or reconcile the attending doctor change according to its supported workflow. A55 should not be treated as a new patient admission, transfer, or general demographic update. Understanding A55 within the broader HL7 ADT messaging framework helps integration teams distinguish provider assignment changes from cancellations.

Purpose of the HL7 A55 Event

A55 communicates that an earlier attending doctor change has been canceled. The destination uses this notification to reconcile the provider assignment while preserving the patient encounter and its administrative history.

When Is an ADT A55 Message Generated?

An A55 notification may be generated when a physician reassignment was entered incorrectly, applied to the wrong encounter, or withdrawn through an authorized patient administration process.

Which Healthcare Systems Receive A55 Messages?

EHRs, hospital information systems, registration applications, care coordination platforms, and clinical documentation systems may receive A55 notifications when they support attending doctor change cancellations.

How A55 Supports Provider Assignment Accuracy

A55 helps connected applications correct attending doctor information after an invalid reassignment. Accurate processing reduces discrepancies in encounter records, administrative reporting, and clinical documentation workflows.

Why Accurate A55 Processing Matters

An incorrect cancellation can restore an outdated provider assignment or overwrite a later valid change. Receiving applications must validate the original event, provider identifiers, encounter ownership, and event sequence.

HL7 ADT A55 Message Structure and Segments

HL7 A55 follows the segment-based format defined by HL7 Version 2. The message identifies the cancellation event, patient, and affected encounter. In HL7 v2.5, A55 uses the ADT_A52 message structure. Important segments include MSH, EVN, PID, and PV1, with additional segments depending on the supported HL7 version and implementation profile.

PV1-7 represents the attending doctor associated with the encounter. The destination must determine how the cancellation relates to the original A54 event rather than assuming that any provider value in PV1-7 is automatically the previous attending doctor.

MSH Segment: Message Header

MSH identifies the sender, receiver, message timestamp, trigger event, message control identifier, and HL7 version. MSH-9 identifies the A55 cancellation event.

EVN Segment: Event Information

EVN records administrative event information, including the recorded date and time. It supports audit tracking and reconciliation with the original attending doctor change.

PID Segment: Patient Identification

PID identifies the patient associated with the cancellation. Receiving applications should verify patient identifiers and assigning authorities before modifying provider assignments.

PV1 Segment: Patient Visit Information

PV1 provides encounter context, including patient class, location, attending doctor, and visit number. It helps the destination identify the affected encounter.

PV1-7: Attending Doctor

PV1-7 contains attending doctor information. The destination should interpret this field according to the interface specification and reconcile it with the original A54 event.

HL7 ADT A55 Message Example With Field Explanation

Consider a hospital where patient Olivia Martin is receiving inpatient care. The encounter is identified by visit number VIS550001. The registration system previously changed the attending doctor from Dr. Robert Smith to Dr. Emily Carter through an A54 event. Staff subsequently discover that the change was entered incorrectly. An authorized user cancels the earlier provider change, and the source generates an A55 notification. The receiving EHR must identify the original change and reconcile the attending doctor assignment.

Complete HL7 ADT A55 Sample Message

MSH|^~\&|REGISTRATION|HOSPITAL|EHR|MAIN|20261022190000||ADT^A55^ADT_A52|MSG55001|P|2.5
EVN|A55|20261022185500
PID|1||MRN550001^^^HOSPITAL^MR||MARTIN^OLIVIA||19890312|F
PV1|1|I|WARD4^ROOM12^BED1||||1234^SMITH^ROBERT||||||||||||VIS550001^^^HOSPITAL^VN

All patient and provider information is fictional. This example assumes the sender's implementation profile places the restored attending doctor in PV1-7.

The canceled assignment is scenario context, not a separate field explicitly carried in this sample A55 message.

Explore each segment and its key fields:

MSH Segment Explained

MSH identifies REGISTRATION as the sending application and EHR as the destination. ADT^A55^ADT_A52 identifies the attending doctor change cancellation event and its message structure.

EVN Segment Explained

EVN records the cancellation event and its timestamp. The destination can use this information to reconcile the A55 notification with the original A54 event.

PID-3: Patient Identifier Explained

PID-3 contains MRN550001, the patient identifier associated with the encounter. The receiving application uses this value to locate the correct patient.

PV1-7: Attending Doctor Explained

PV1-7 contains Dr. Robert Smith's provider information in this example. The destination must validate the intended restored assignment against the original provider change and interface agreement.

PV1-19: Visit Number Explained

PV1-19 identifies encounter VIS550001. The receiving application should verify the visit and its assigning authority before processing the cancellation.

Important HL7 ADT A55 Fields and Mapping

Accurate A55 integration depends on identifying the correct patient, encounter, original provider change, and intended attending doctor assignment. MSH-9 identifies the cancellation event, while MSH-10 supports message tracking. PID-3 identifies the patient, PV1-7 represents the attending doctor, and PV1-19 identifies the encounter where supported.

The receiving application should preserve complete provider identifier context and verify the relationship to the original A54 event.

PV1-7.1: Attending Doctor Identifier

PV1-7.1 contains the provider identifier. The destination should resolve this value within the correct identifier domain before changing the attending doctor assignment.

PV1-7.2 and PV1-7.3: Provider Name

PV1-7.2 and PV1-7.3 commonly contain the provider's family and given names. These values support display and reconciliation but should not replace authoritative provider identifier matching.

PV1-19: Encounter Identification

PV1-19 identifies the visit associated with the cancellation. It helps prevent a valid A55 notification from being applied to the wrong encounter.

PID-3: Patient Identity

PID-3 provides the patient identifier. Complete identifier context, including assigning authority, should be preserved to prevent collisions between facilities.

MSH-10: Message Control Identifier

MSH-10 identifies the A55 message for acknowledgment correlation, duplicate detection, and audit tracking. It does not automatically identify the original A54 message being canceled.

How HL7 ADT A55 Attending Doctor Cancellation Workflows Operate

An A55 workflow begins when an authorized user determines that a previously recorded attending doctor change must be canceled. The source application identifies the original provider reassignment and affected patient encounter. It validates the cancellation and generates an A55 notification.

An integration engine routes the message to connected applications. The receiving system locates the original A54 event, verifies whether cancellation is permitted, and reconciles the attending doctor assignment.

Step 1: Identify the Original Attending Doctor Change

The source identifies the earlier provider reassignment that requires cancellation. Authorized staff verify the affected patient, encounter, and original assignment.

Step 2: Validate the Cancellation Request

The source confirms that the previous change was recorded incorrectly or withdrawn. It also checks whether later provider changes affect the requested cancellation.

Step 3: Generate the A55 Notification

The source creates an A55 message containing patient, encounter, provider, and cancellation event information according to the supported implementation profile.

Step 4: Validate and Route the Message

An integration engine checks the trigger event, identifiers, and routing rules. The notification is forwarded to the destination responsible for maintaining attending doctor assignments.

Step 5: Reconcile and Acknowledge the Cancellation

The destination validates the original event and applies the approved correction. It then returns an acknowledgment and records the result for audit and troubleshooting.

How to Implement HL7 ADT A55 Messages Using Mirth Connect

Mirth Connect can receive, validate, transform, and route HL7 A55 messages between hospital registration systems, EHRs, provider management applications, and other healthcare platforms. A typical workflow receives the cancellation through an MLLP listener, verifies the A55 trigger event, extracts patient and encounter identifiers, and forwards the request to an authorized destination.

The receiving application must verify the original attending doctor change before applying the cancellation. The integration engine should not independently determine which historical provider assignment to restore without an authoritative record.

Configure the Mirth Connect Source Connector

Create a channel using an MLLP Listener and HL7 v2.x inbound data type. Configure authorized senders, transport security, acknowledgment behavior, message retention, and destination routing based on the interface specification.

Filter HL7 ADT A55 Messages

Use a JavaScript filter to identify A55 events and reject unrelated messages from the cancellation workflow.

var messageType =
    msg['MSH']['MSH.9']['MSH.9.1'].toString();

var triggerEvent =
    msg['MSH']['MSH.9']['MSH.9.2'].toString();

var version =
    msg['MSH']['MSH.12']['MSH.12.1'].toString();

return messageType === 'ADT' &&
       triggerEvent === 'A55' &&
       version === '2.5';

This example assumes HL7 v2.5. Production interfaces should additionally validate the agreed message structure, sending facility, required segments, and applicable implementation profile.

Extract Patient, Encounter, and Provider Information

Use a JavaScript transformer to extract patient identity, visit number, attending doctor details, and cancellation metadata.

function getComponent(segment, field, component) {
    var fieldName = segment + '.' + field;
    var componentName = fieldName + '.' + component;

    var fieldNode = msg[segment][fieldName];

    if (fieldNode.length() === 0) {
        return '';
    }

    var componentNode = fieldNode[componentName];

    if (componentNode.length() === 0) {
        return '';
    }

    return componentNode.toString().trim();
}

var messageType = getComponent('MSH', 9, 1);
var triggerEvent = getComponent('MSH', 9, 2);
var version = getComponent('MSH', 12, 1);

var patientId = getComponent('PID', 3, 1);
var patientAuthority = getComponent('PID', 3, 4);

var visitNumber = getComponent('PV1', 19, 1);
var visitAuthority = getComponent('PV1', 19, 4);

var attendingId = getComponent('PV1', 7, 1);
var attendingFamilyName = getComponent('PV1', 7, 2);
var attendingGivenName = getComponent('PV1', 7, 3);

var controlId = getComponent('MSH', 10, 1);
var eventTimestamp = getComponent('EVN', 2, 1);

var sendingApplication = getComponent('MSH', 3, 1);
var sendingFacility = getComponent('MSH', 4, 1);

if (messageType !== 'ADT' ||
    triggerEvent !== 'A55' ||
    version !== '2.5') {
    throw new Error(
        'Unsupported HL7 event or version'
    );
}

if (!patientId || !visitNumber) {
    throw new Error(
        'Missing patient or encounter identifier'
    );
}

if (!controlId || !eventTimestamp) {
    throw new Error(
        'Missing message control ID or event timestamp'
    );
}

var cancellation = {
    eventType: 'A55',
    action: 'cancelAttendingDoctorChange',

    patient: {
        identifier: patientId,
        assigningAuthority: patientAuthority
    },

    encounter: {
        visitNumber: visitNumber,
        assigningAuthority: visitAuthority
    },

    reportedAttendingDoctor: {
        identifier: attendingId,
        familyName: attendingFamilyName,
        givenName: attendingGivenName
    },

    sourceEvent: {
        application: sendingApplication,
        facility: sendingFacility,
        hl7Version: version,
        messageControlId: controlId,
        timestamp: eventTimestamp
    }
};

channelMap.put(
    'attendingCancellation',
    JSON.stringify(cancellation)
);

This example extracts the first occurrence of each identifier. Production implementations should preserve full assigning authority details, handle relevant repetitions, and interpret the attending doctor field according to the sender's implementation profile.

Transform A55 Into a Cancellation Request

Create a destination-specific payload that preserves the encounter, reported provider information, and source event metadata.

var event = JSON.parse(
    channelMap.get('attendingCancellation')
);

var request = {
    eventType: 'A55',
    action: 'requestAttendingChangeCancellation',

    patient: event.patient,
    encounter: event.encounter,

    reportedAttendingDoctor:
        event.reportedAttendingDoctor,

    processingStatus:
        'pending_original_change_validation',

    sourceEvent: event.sourceEvent
};

channelMap.put(
    'jsonPayload',
    JSON.stringify(request)
);

This JSON payload is illustrative, not a standardized HL7 API. The destination must determine which original attending doctor change is being canceled and verify the appropriate resulting assignment.

Validate the Original A54 Event

Confirm that the encounter has a matching attending doctor change eligible for cancellation. Check the original provider assignment and any later changes before deciding whether restoration is appropriate.

Configure Destination Processing and Monitoring

Use an approved EHR API or supported HL7 interface. Configure duplicate detection, controlled retries, acknowledgment processing, exception queues, and alerts for unresolved provider assignment cancellations.

HL7 ADT A55 ACK Message Examples and Error Handling

HL7 acknowledgments communicate whether an A55 message was accepted or rejected according to the configured processing agreement. A typical acknowledgment includes MSH and MSA segments. ERR may provide additional details when validation or application processing fails.

In original acknowledgment mode, AA indicates application acceptance, AE indicates an application error, and AR indicates rejection. An acknowledgment does not necessarily confirm that every downstream application has completed the provider assignment correction.

Successful A55 ACK: AA

An AA acknowledgment indicates application acceptance under the configured mode. MSA-2 references the original A55 message control identifier.

MSH|^~\&|EHR|MAIN|REGISTRATION|HOSPITAL|20261022190001||ACK^A55^ACK|ACK55001|P|2.5
MSA|AA|MSG55001

Application Error ACK: AE

An application error may occur when the destination cannot locate the original attending doctor change or reconcile the encounter's provider assignment.

MSH|^~\&|EHR|MAIN|REGISTRATION|HOSPITAL|20261022190002||ACK^A55^ACK|ACK55002|P|2.5
MSA|AE|MSG55001
ERR|||204^Unknown Key Identifier^HL70357|E

The ERR value is illustrative. Production error codes and messages must follow the receiving application's interface profile.

Application Rejection ACK: AR

An AR acknowledgment indicates rejection. Unsupported events, unauthorized sending applications, or invalid message structures may cause the destination to reject an A55 notification.

MSH|^~\&|EHR|MAIN|REGISTRATION|HOSPITAL|20261022190003||ACK^A55^ACK|ACK55003|P|2.5
MSA|AR|MSG55001

Correlate Acknowledgments With Original Messages

MSA-2 should match the original A55 message's MSH-10 identifier. Monitoring records should associate each response with the patient, encounter, provider information, and processing result.

Handle Failed Acknowledgments and Safe Retries

Before resending an unacknowledged A55 message, determine whether the destination already applied the cancellation. Repeated processing must not overwrite a later valid attending doctor assignment.

Common HL7 ADT A55 Integration Errors and Troubleshooting

HL7 A55 integration failures commonly involve missing original A54 events, incorrect encounter matching, provider identifier mismatches, and out-of-order messages. A receiving system may have processed the original provider change but subsequently received another valid assignment. Blindly restoring a historical provider could overwrite the current attending doctor.

Other failures occur when an integration engine interprets A55 as a new A54 event or assumes that PV1-7 alone identifies the canceled assignment. Accurate field mapping and administrative event reconciliation are essential.

Original A54 Change Cannot Be Found

The destination may not have received or retained the original attending doctor change. Review message logs, provider assignment history, and encounter records before applying the cancellation.

A55 Is Processed as a New A54 Event

A55 cancels an earlier change, while A54 communicates a new attending doctor assignment. Treating them identically may apply the wrong provider to the encounter.

PV1-7 Provider Identifier Is Incorrect

An incorrect provider identifier or mismatched identifier domain may prevent the destination from resolving the attending doctor. Validate the identifier against the authoritative provider directory.

A Later Provider Assignment Already Exists

An A55 notification may arrive after another valid provider change. Reconcile the event history and current assignment before restoring any earlier provider information.

Duplicate A55 Messages Cause Repeated Updates

Retries and message replay may deliver the same cancellation multiple times. Implement idempotency so repeated messages do not generate additional provider changes or unnecessary downstream notifications.

HL7 ADT A55 vs A54, A08, A02, and A13

HL7 Version 2 includes separate administrative events for attending doctor changes, cancellation of attending doctor changes, general patient information updates, transfers, and discharge cancellations. These events represent different administrative actions. A55 specifically cancels an earlier attending doctor change.

A55 vs A54: Cancellation and Assignment

A54 communicates a change in attending doctor, while A55 cancels a previously recorded change. The receiving application should validate the original A54 event before processing A55.

A55 vs A08: Cancellation and General Update

A08 communicates general patient or visit information updates. A55 has a specific cancellation meaning and may require historical provider assignment reconciliation.

A55 vs A02: Provider Cancellation and Transfer

A02 communicates a patient transfer, while A55 cancels an attending doctor change. A provider reassignment may accompany a transfer, but these events have different meanings.

A55 vs A13: Provider and Discharge Cancellations

A55 cancels an attending doctor change, while A13 cancels a discharge. These events affect different administrative records and require separate processing rules.

Best Practices for Reliable HL7 A55 Integration

Reliable A55 integration requires validation of the original attending doctor change, accurate provider identification, and careful handling of event history. Healthcare organizations should define the authoritative source for attending doctor assignments and document how receiving systems interpret cancellations.

Interfaces should handle duplicate messages, delayed delivery, subsequent provider changes, and differences between provider identifier systems.

Validate the Original Provider Change

Confirm that the original A54 event exists and is eligible for cancellation. Do not restore a historical attending doctor solely because an A55 notification was received.

Preserve Attending Doctor Assignment History

Retain original provider changes, cancellations, and subsequent assignments. Historical information supports audits, administrative reporting, clinical documentation review, and troubleshooting.

Use Authoritative Provider Identifiers

Resolve providers using structured identifiers and assigning authorities. Provider names alone are insufficient because names can be duplicated or represented differently across applications.

Implement Event Sequencing and Idempotency

Track message identifiers and provider assignment history. Reconcile delayed or repeated cancellations before updating the current attending doctor.

Monitor Downstream Provider Consistency

Confirm that EHRs, documentation systems, and administrative applications reflect the authorized assignment. Route unresolved discrepancies to a monitored exception workflow.

Frequently Asked Questions About HL7 ADT A55 Messages

HL7 A55 integration raises questions about canceling attending doctor changes, PV1-7 mapping, original A54 events, and provider assignment reconciliation. The following answers address common implementation requirements.

Need Help With HL7 ADT A55 Integration?

Attending doctor change cancellations require coordination between registration systems, EHRs, provider directories, clinical documentation applications, and administrative platforms. Taction Software supports HL7 interface development, Mirth Connect configuration, provider identifier mapping, and healthcare interoperability.

Our engineers can help organizations implement A55 workflows, investigate provider assignment discrepancies, and establish monitoring and reconciliation procedures.

HL7 Attending Doctor Cancellation Interfaces

We develop HL7 A55 interfaces based on source and destination requirements, including provider mapping, original event validation, encounter matching, and controlled cancellation processing.

Mirth Connect Development and Integration

Our engineers configure Mirth Connect channels for attending doctor change cancellations, including JavaScript transformations, secure routing, acknowledgment handling, and exception management.

EHR and Provider Directory Integration

We support integration between EHRs, registration systems, provider directories, and clinical applications using approved attending doctor assignment and cancellation workflows.

Production Monitoring and Troubleshooting

We help investigate failed cancellations, missing original events, provider identifier mismatches, acknowledgment errors, and inconsistent downstream attending doctor assignments.

Need help with HL7 ADT integration? Visit HL7 Integration or explore Taction Software's EHR integration services to discuss your requirements.