HL7 BUI Segment: Blood Unit Information

The BUI (Blood Unit Information) segment was introduced in HL7 v2.7 and carries the physical and identifying attributes of a blood-bank unit — the unit identifier, product type, weight, volume, container catalog and lot numbers, manufacturer, and transport temperature. It travels in blood-bank product status and dispense messages alongside BPO and BPX.

Purpose

BUI describes a single physical blood unit as it moves through the blood-bank workflow. It is distinct from BPO (the product order) and BPX (the dispense event): BUI specifies the unit's intrinsic properties (what it weighs, what it contains, how it must be transported) so a downstream system can validate, label, and track the unit.

Used in

BPS — Blood Product Dispense Status — the primary carrier message for BUI, where one or more BUI segments accompany each product group.
Blood-bank product status update messages (BRP, BRT).
Custom blood-bank workflows that exchange unit-level attributes between LIS, transfusion service, and EHR.

Field-by-field reference

Source: HAPI HL7v2 v2.8.1 javadocs (BUI) for sequence, name, data type, and repetition. Length is not published in the javadocs (—); Required and Table # are filled from the HL7 v2 standard where well-established.

Seq	Name	Data Type	Length	Req	Repeat	Table #	Description
BUI-1	Set ID – BUI	si	—	R	—	—	Sequence number for BUI repetitions.
BUI-2	Blood Unit Identifier	ei	—	O	—	—	Unique identifier assigned to the blood unit.
BUI-3	Blood Unit Type	cwe	—	O	—	—	Coded product type, e.g. red blood cells.
BUI-4	Blood Unit Weight	nm	—	O	—	—	Numeric weight of the unit.
BUI-5	Weight Units	cne	—	O	—	—	Units of measure for the weight.
BUI-6	Blood Unit Volume	nm	—	O	—	—	Numeric volume of the unit.
BUI-7	Volume Units	cne	—	O	—	—	Units of measure for the volume.
BUI-8	Container Catalog Number	st	—	O	—	—	Manufacturer catalog number for the container.
BUI-9	Container Lot Number	st	—	O	—	—	Container lot number for traceability.
BUI-10	Container Manufacturer	xon	—	O	—	—	Organization that produced the container.
BUI-11	Transport Temperature	nr	—	O	—	—	Allowed transport temperature range.
BUI-12	Transport Temperature Units	cne	—	O	—	—	Units of measure for the temperature range.

Most-used fields

BUI-1 Set ID — required, increments when multiple BUI segments accompany one product.
BUI-2 Blood Unit Identifier — the DIN-derived or facility-assigned unit ID used downstream.
BUI-3 Blood Unit Type — coded product type that drives compatibility and labeling.
BUI-6 / BUI-7 Volume + Units — the most-validated physical attribute downstream of dispense.
BUI-11 / BUI-12 Transport Temperature + Units — cold-chain validation at receipt.

Version differences

HL7 v2.7 — BUI introduced. All twelve fields defined as listed above.
HL7 v2.7.1, v2.8, v2.8.1, v2.8.2 — no structural changes; field list and data types remain stable per the HAPI v2.8.1 javadocs.

Common mistakes

Sending volume in BUI-6 without populating BUI-7 Volume Units — downstream validators reject the unit because units are ambiguous.
Reusing BPO-3 Blood Product Identifier in BUI-2 — BUI-2 is the unit identifier (often the DIN), not the product order ID.
Free-text product names in BUI-3 instead of a coded value from a recognized blood-product code system.
Omitting BUI-1 Set ID when more than one BUI accompanies a product group.
Sending a single point temperature in BUI-11 — the field is NR (numeric range), so send low^high.

Examples

Minimal:

BUI|1|W123426789012^^^RedCrossBB^DIN|E0336^RBC LR^HL70435

Fully populated:

BUI|1|W123426789012^^^RedCrossBB^DIN|E0336^RBC LR^HL70435|312|g^gram^UCUM|285|mL^milliliter^UCUM|REF-4R5400|LOT-88241A|Acme BioContainers Inc.^^^^^FDA^XX^^^1188291|1^6|Cel^degree Celsius^UCUM

Annotated breakdown:

BUI                              Segment ID
|1                               BUI-1  Set ID
|W123426789012^^^RedCrossBB^DIN  BUI-2  Blood Unit Identifier (EI; DIN)
|E0336^RBC LR^HL70435            BUI-3  Blood Unit Type (CWE; ISBT 128 product code)
|312                             BUI-4  Blood Unit Weight (NM)
|g^gram^UCUM                     BUI-5  Weight Units (CNE)
|285                             BUI-6  Blood Unit Volume (NM)
|mL^milliliter^UCUM              BUI-7  Volume Units (CNE)
|REF-4R5400                      BUI-8  Container Catalog Number (ST)
|LOT-88241A                      BUI-9  Container Lot Number (ST)
|Acme BioContainers Inc.^...     BUI-10 Container Manufacturer (XON)
|1^6                             BUI-11 Transport Temperature (NR; low^high)
|Cel^degree Celsius^UCUM         BUI-12 Transport Temperature Units (CNE)

In context — BPS^O29 blood-bank product dispense status:

MSH|^~&|TXM|MERCY^2.16.840.1.113883.19.5.99999.1^ISO|LIS|MERCY|20260610091500||BPS^O29^BPS_O29|MSG00041|P|2.8.1
PID|1||MR884412^^^MERCY^MR||TESTPATIENT^ALEX^Q||19720508|F
ORC|SC|TR-7741|||CM
BPO|1|E0336^RBC LR^HL70435|1|U^unit^UCUM
BPX|1|DI|W123426789012^^^RedCrossBB^DIN|RC|||20260610092200
BUI|1|W123426789012^^^RedCrossBB^DIN|E0336^RBC LR^HL70435|312|g^gram^UCUM|285|mL^milliliter^UCUM|REF-4R5400|LOT-88241A|Acme BioContainers Inc.|1^6|Cel^degree Celsius^UCUM

In context — multiple BUI repetitions for a split unit:

MSH|^~&|BB|MERCY|EHR|MERCY|20260610100300||BPS^O29^BPS_O29|MSG00042|P|2.8.1
ORC|SC|TR-7742|||CM
BPO|1|E0336^RBC LR^HL70435|2|U^unit^UCUM
BPX|1|DI|W123426789012001^^^RedCrossBB^DIN|RC
BPX|2|DI|W123426789012002^^^RedCrossBB^DIN|RC
BUI|1|W123426789012001^^^RedCrossBB^DIN|E0336^RBC LR^HL70435|158|g^gram^UCUM|142|mL^milliliter^UCUM
BUI|2|W123426789012002^^^RedCrossBB^DIN|E0336^RBC LR^HL70435|154|g^gram^UCUM|143|mL^milliliter^UCUM

FHIR mapping

No segment-level ConceptMap is published in the v2-to-FHIR IG for BUI. Conceptually, BUI attributes map to BiologicallyDerivedProduct:

BUI-2 → BiologicallyDerivedProduct.identifier
BUI-3 → BiologicallyDerivedProduct.productCode
BUI-4 / BUI-5 → BiologicallyDerivedProduct.weight
BUI-6 / BUI-7 → BiologicallyDerivedProduct.volume (typically a custom extension or quantity)
BUI-8 / BUI-9 / BUI-10 → BiologicallyDerivedProduct.collection and container extensions
BUI-11 / BUI-12 → BiologicallyDerivedProduct.storage / processing-temperature extension

Mapping at the resource level rather than the segment level is consistent with how blood-bank workflows are modeled in FHIR R4/R5.

Engine considerations

Routing engines that pre-date v2.7 (Mirth Connect ≤ 2.x, older Cloverleaf table sets) will parse BUI as an unknown Z-segment unless the schema is upgraded — load a v2.7+ profile before brokering.
HAPI HL7v2 v2.8.1 generates ca.uhn.hl7v2.model.v281.segment.BUI with strongly-typed accessors; lower-version structures must use HAPI's GenericSegment.
BUI-11 is an NR (numeric range) — many engines stringify it as low^high; ensure schema validation accepts the caret without flagging it as a component delimiter error.
BUI repetitions accompany product-group repetitions inside the BPS_O29 structure; engines that flatten product groups risk losing the BUI ↔ BPX correlation.

How Vorro parses and produces BUI

Vorro's blood-bank pipeline treats BUI as a unit-attribute carrier bound to the surrounding BPX dispense. On inbound:

BUI-1 Set ID is used to align each BUI to its sibling BPX within the same product group; we do not assume a 1:1 ordering and instead match on BUI-2 ↔ BPX-3 (the DIN).
BUI-3 is normalized against ISBT 128 product-code and HL70435 tables; unmapped codes are routed to a curation queue rather than silently dropped.
BUI-4 / BUI-5 and BUI-6 / BUI-7 are validated for unit consistency (UCUM g, mL) and converted to primary UCUM internally.
BUI-11 is parsed as low^high; a single point value is accepted but flagged as a soft warning.

On outbound, Vorro emits BUI with stable Set IDs starting at 1, always pairs values with explicit UCUM units, and renders manufacturer identifiers as XON with an FDA-issued organization ID where available.

Sources

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