HL7 SSR_U04 Specimen Status Request

A targeted question: where is this container or specimen right now?
HL7 message structure SSR_U04 groups and segments from HL7 v2.5.1 Hide structure

These are the generated groups and segments for the version selected at the top of the page. The article explains the workflow, and this panel follows the chosen HL7 version.

Message Structure

SegmentNameRequiredRepeatable
MSH
 Message Header Yes No
SFT
 Software Segment No Yes
EQU
 Equipment Detail Yes No
SSR_U04.SPECIMEN_CONTAINER
 Specimen Container group Yes Yes
SAC
 Specimen Container detail Yes No
SPM
 Specimen No Yes
ROL
 Role No No

SSR_U04 asks automated equipment or middleware for specimen status. A Laboratory Automation System sends it when it needs the current location or state of a container, tray, carrier, or specimen instead of waiting for the next unsolicited update.

The useful response is SSU_U03. The ACK only confirms message handling; the SSU response carries the specimen status information.

A small SSR U04 example

MSH|^~\&|LAS|CITYHOSP|TRACK01|CORELAB|20260723101600||SSR^U04^SSR_U04|SSR040001|P|2.5.1 EQU|TRACK01^Automation Track 1^CITYHOSP|20260723101600 SAC|||TUBE12345^CITYHOSP|||||||RACK^Rack^L|RACK7|04 SPM|1|SPEC12345^CITYHOSP||SER^Serum^HL70487

What workflow it represents

Use SSR_U04 when the receiver needs a current status snapshot for a specific physical target. The request might point to a specimen container, a carrier, a tray position, or a location, depending on the SAC values agreed in the profile.

It is useful after downtime recovery, when an operator searches for a missing container, or when middleware needs to reconcile its local state with the automation line.

How to read the structure

MSH identifies the request. Optional SFT can describe the requester. Required EQU identifies the equipment or automation component being asked.

Each SPECIMEN_CONTAINER group contains required SAC, which supplies the container, carrier, tray, or location arguments for the request. Optional repeating SPM rows can narrow the request to specimen-level identity.

Implementation traps

Be precise about what the SAC arguments mean. A request for a tube, a rack, a tray position, and a physical location are different questions, even if all of them travel in the same segment family.

Do not rebuild state from the ACK. Wait for the SSU_U03 response, or define a timeout and exception path if the equipment cannot answer.

If the request can return multiple containers, make sure the receiver expects multiple SPECIMEN_CONTAINER groups in the SSU_U03 response. A single-row assumption turns reconciliation into guesswork.

Reference notes

HL7 v2+ describes SSR_U04 as a request for specimen location and status. The request can target a specific container, carrier, tray, or location based on the SAC arguments, and the identified equipment should respond with SSU_U03.