ADT^A21 — Patient Goes on a 'Leave of Absence'
The patient leaves temporarily (weekend pass, long external exam, family event): A21 pauses the encounter without closing it. A22 brings the patient back.
Purpose
LOA is the administrative pause of an encounter. Typical cases: prescribed leave pass, long external exam (PET scan at another facility), recent family bereavement. Bed stays reserved, pharmacy suspends doses, the HIS does not bill the absent day (per local regulation).
PV1-2 should reflect LOA via the appropriate combination. Many EHRs use PV1-41 (Account Status) or a dedicated OBX to mark LOA. Exit from LOA uses A22 (Patient Returns from LOA).
Segment structure
Structure ADT_A21: MSH, EVN, PID, PV1 (+ PV2, OBX optional).
Real-world example
Patient John Doe on leave pass on 17 May at 10:00:
MSH|^~\&|HIS|HOSP01|EHR|CLINIC02|20260517100000||ADT^A21^ADT_A21|MSG00021001|P|2.5.1|||AL|NE
EVN|A21|20260517100000|||DRJONES^Jones^Sarah^^^DR.
PID|1||MRN567890^^^HOSP^MR||DOE^JOHN^A^^MR.||19720515|M
PV1|1|I|MED^205^A^HOSP01|EM|||DRSMITH^Smith^James^A^^DR.|||MED|||1|||DRSMITH|ADM|||||||||||||||||||HOSP01|||||20260514102530Acknowledgment (ACK)
MSH|^~\&|EHR|CLINIC02|HIS|HOSP01|20260517100001||ACK^A21^ACK|ACK00021001|P|2.5.1
MSA|AA|MSG00021001Common errors
- A21 without A22 within 48h: some EHRs auto-close the encounter; risks turning a leave pass into an unintended definitive discharge.
- A03 emitted during LOA: closes the encounter, A22 no longer knows where to bring the patient back.
- Pharmacy keeps dispensing: the pharmacy system must interpret A21 to suspend scheduled administrations.
Related ADT events
| Code | Trigger event | Description |
|---|---|---|
| A21 | Patient Goes on LOA | This page. |
| A22 | Patient Returns from LOA | Leave return. |
| A52 | Cancel Leave of Absence for a Patient | Cancellation of A21. |
| A53 | Cancel Patient Returns from LOA | Cancellation of A22. |