HL7 INR Messages: Automated Equipment Inventory Request

HL7 INR messages ask a piece of laboratory automation equipment for its current inventory — the reagents, consumables, calibrators, and containers it currently has on board, along with their lot numbers, expiration dates, and on-hand quantities. An INR message is the request half of an inventory exchange between a controlling system and a lab automation instrument: the controller sends INR to ask "what do you have right now?" and the instrument answers with an INU inventory update response. This page explains what an INR message represents, the trigger event that carries it, every segment the message can contain and what each one holds, and how an INR inventory request relates to FHIR. Sample content is constructed for illustration with fictional identifiers.

What an INR message represents

An INR message — INR stands for Automated Equipment Inventory Request — communicates a request from a controlling system to laboratory automation equipment for the current state of one or more inventory substances. The two core segments are EQU, which identifies the equipment being queried and its current operational state, and INV (Inventory Detail), which identifies each substance the controller wants information about — the reagent, consumable, or container by substance identifier, along with the type, container/carrier position, quantity, lot, expiration, and manufacturer fields the response will populate. Each repeating INV names one inventory substance the controller is asking the instrument about.

INR is part of HL7 Chapter 13, Laboratory Automation — the chapter that defines the messages exchanged between a laboratory automation manager and the instruments and pre-analytical equipment it controls. The sender is the controlling system (the laboratory automation manager or middleware), and the receiver is the automation equipment itself (the analyzer, sorter, or pre-analytical device). Because INR is a request and not a state change, the equipment does not act on the inventory based on the message — it gathers the requested values and returns them in the matching INU response.

When an INR message is sent

An INR message is sent when a controlling system needs the current inventory state of laboratory automation equipment. Typical triggers are a scheduled inventory poll, an operator-initiated stock check, a low-reagent alert that needs to be confirmed against the instrument's own count, or a pre-run readiness check before a batch is queued. The controller composes an INR naming the equipment in EQU and the substances it wants reported in one or more INV segments, and the equipment replies with an INU carrying the matching values.

Trigger event

The INR message type carries a single trigger event:

• INR^U06 – Automated equipment inventory request.

Because INR has one trigger event, the receiver's handling turns on the equipment identifier in EQU and the substances listed in INV — which inventory items the controller is asking about — rather than on the trigger code in MSH-9.

Integration topology

The diagram shows the laboratory automation manager issuing an inventory request through the integration engine to the instrument, which replies with an INU update.

{{diagram: lab automation manager → INR request → integration engine → lab automation equipment → INU response → integration engine → lab automation manager}}

Typical senders: laboratory automation manager, laboratory middleware, instrument-control application.

Typical receivers: the laboratory automation equipment whose inventory is being requested — analyzer, pre-analytical sorter, aliquoter, or other Chapter 13 device.

Direction: the request leg of a synchronous request-response exchange — the INR travels from the controlling system to the instrument, which answers with INU^U05.

Segments in an INR message

The INR_U06 message opens with MSH, optionally carries software-identification in SFT, names the equipment in EQU, and then carries one or more INV inventory detail segments — one per substance the controller is asking about — closing with an optional ROL. Cardinality follows HL7 notation: [X] optional, {X} repeating, [{X}] optional and repeating; a bare code is required. Each segment code links to its canonical field-by-field reference.

[ ] = optional, { } = repeating

The INV segment repeats once per substance requested, so a single INR message can ask about many items on one piece of equipment in a single exchange. The canonical segment pages carry the full field-by-field detail.

Sample INR message

Note. Constructed for illustration. Equipment identifiers, substance codes, and dates are fictional.

MSH|^~&|LAB_MGR|MERCYGEN|ANALYZER01|MERCYGEN|202006150930||INR^U06^INR_U06|MSG00078|P|2.5.1
EQU|ANALYZER01^MERCYGEN^EUI|202006150930
INV|R123^Glucose Reagent^L
INV|R124^Sodium Reagent^L

What this sample shows

The INR^U06 in MSH-9 marks an automated equipment inventory request. EQU identifies the target device as ANALYZER01 (EQU-1) and stamps the request at 202006150930 (EQU-2); the optional state, control, and alert-level fields (EQU-3 through EQU-5) are left empty in this request since the controller is asking for inventory, not reporting equipment status. The two INV segments ask about two substances by identifier (INV-1): R123 Glucose Reagent and R124 Sodium Reagent. The quantitative fields — quantities, units, container/carrier, lot, and expiration — are left empty in the request; the equipment will populate them in its INU^U05 response.

Working with INR messages

Pin the request to one device through EQU-1

EQU-1 is the equipment instance identifier and the only thing scoping the inventory request to a specific device. When a controller manages many instruments through one integration channel, EQU-1 is what the equipment uses to recognize the request is for it and what the controller uses to correlate the INU response. Treat it as the conversation key.

List each substance with its own INV

INV repeats once per substance, and each segment names one item. A controller asking about reagents and consumables in the same poll sends one INV per substance, not a comma-separated list — the equipment's response will repeat the same INV structure with the quantitative and provenance fields populated.

Treat the request as identifying, not quantitative

In an INR, the controller populates the identifying fields of INV (typically INV-1 substance identifier, optionally INV-3 substance type) and leaves the status, quantity, container/carrier, lot, and expiration fields empty. Those fields belong to the equipment's response. Sending a value in INV-8 (current quantity) or INV-12 (expiration date/time) on a request can confuse receivers that expect those fields to be empty until they answer.

Match the response by message control id and EQU-1

The matching INU^U05 reply carries the equipment identifier in its own EQU-1 and acknowledges the request through MSH-10 in the ACK. Correlate the response by both, since an instrument may have a queued earlier inventory update in flight that is not the answer to the request just sent.

Vendor variance. The Chapter 13 segments EQU and INV have wide vendor variance. Some analyzers populate EQU-3 through EQU-5 with rich state and alert detail; others send only EQU-1 and EQU-2. Some controllers identify substances by INV-1 substance identifier only; others additionally constrain by INV-3 substance type. Confirm a partner's field usage against their interface specification rather than assuming the base standard.

FHIR equivalent

Laboratory automation inventory management is outside FHIR's clinical scope, and there is no published mapping to lean on. The HL7 v2-to-FHIR Implementation Guide provides no message map for INR_U06 and no ConceptMap for the EQU or INV segments.

Conceptually, the inventory substances requested by INV — reagents, consumables, and calibrators identified by substance identifier, lot, and expiration — map to the FHIR Substance resource, and the equipment identified by EQU maps to a Device resource. A FHIR representation of an INR exchange (querying Substance instances on a Device) is composed manually, since neither the message nor its segments have a published map.

Common pitfalls

Pitfall. Sending an INR without an equipment instance identifier in EQU-1. The request has no target; the receiver cannot scope its response and may reject the message.

Pitfall. Populating quantitative fields of INV on the request. Filling INV-8 current quantity, INV-12 expiration date/time, or INV-16 manufacturer lot number on an INR can be read as an assertion rather than a query — those fields belong in the INU response.

Pitfall. Assuming the matching INU lists substances in the order they were requested. An instrument may reorder, group, or omit items it does not recognize; reconcile the response by INV-1 substance identifier rather than by position.

How Vorro handles INR messages

Vorro routes each INR request from the controlling system to the named laboratory automation equipment in EQU-1, preserving the message control id so the matching INU^U05 response can be correlated back. Vorro reads the requested substances from each INV by substance identifier (INV-1), surfaces the equipment state from EQU-3 through EQU-5 for monitoring when populated, and, where a downstream destination needs a different inventory format, transforms the request and the matching response into that system's representation — composed manually, since the v2-to-FHIR Implementation Guide publishes no map for this message or its segments.

Related messages

• EAC — automated equipment command, the Chapter 13 message that instructs equipment to act rather than report.
• ESU — automated equipment status update, the unsolicited equipment-state notification.
• EAN — automated equipment notification, equipment-initiated alerts and notifications.

Sources

• HL7 v2-to-FHIR IG — message maps index — confirms no message map for INR_U06
• HL7 v2-to-FHIR IG — segment maps index — confirms no published ConceptMap for the EQU or INV segments
• HL7 Messaging Standard Version 2.5.1 product brief