HL7 TCD Test Code Detail
HL7 field reference TCD fields from HL7 v2.5.1 Show fields
These are the generated fields for the version selected at the top of the page. The document stays the same, but the reference panel follows that version.
Fields
| Field | Name | Required | Repeatable | Type | Table |
|---|---|---|---|---|---|
| TCD.1 | Universal Service Identifier | Yes | No | CE | |
| TCD.2 | Auto-Dilution Factor | No | No | SN | |
| TCD.3 | Rerun Dilution Factor | No | No | SN | |
| TCD.4 | Pre-Dilution Factor | No | No | SN | |
| TCD.5 | Endogenous Content of Pre-Dilution Diluent | No | No | SN | |
| TCD.6 | Automatic Repeat Allowed | No | No | ID | 0136 |
| TCD.7 | Reflex Allowed | No | No | ID | 0136 |
| TCD.8 | Analyte Repeat Status | No | No | CE | 0389 |
TCD carries test-code detail such as test attributes, units, and timing controls.
The standard describes TCD this way: The test code detail segment contains the data necessary to perform operations or calculations, or execute decisions by the laboratory automation system, and which are not supported by the original HL7 segments related to orders (ORC, OBR). For detail of use see messages of laboratory orders and observations in chapters 4 and 7.
Equipment and specimen-control segments are used around instruments, analyzers, containers, device commands, device status, and test configuration. They are practical plumbing for lab and automation workflows.
The main trap is treating an equipment status as if it were a clinical result, or treating a specimen/container identifier as if it were interchangeable with a patient or order identifier. Keep the layers separate.
The v2.5.1 structures show TCD in OML_O21 - OML - Laboratory order, OML_O33 - OML - Laboratory order for multiple orders related to a single specimen, OML_O35 - OML - Laboratory order for multiple orders related to a single container of a specimen, and OUL_R21 - OUL - Unsolicited laboratory observation, and 3 other message structures. That tells you where it can appear, but the implementation guide still decides which optional fields are meaningful.
For practical interface work, read the generated field panel for datatype, required, repeatable, and table details, then use the notes below to decide what the field should mean in the receiving workflow.
TCD-1 identifies the Universal Service Identifier for this equipment or specimen workflow. Send the identifier that the receiving system actually keys on, and keep the assigning authority or coding system visible when the datatype supports it.
TCD-2 describes specimen or container handling. This is not patient identity and not order identity; it is the physical or analyzer-side detail needed to move, test, store, or track the specimen correctly.
TCD-3 describes specimen or container handling. This is not patient identity and not order identity; it is the physical or analyzer-side detail needed to move, test, store, or track the specimen correctly.
TCD-4 describes specimen or container handling. This is not patient identity and not order identity; it is the physical or analyzer-side detail needed to move, test, store, or track the specimen correctly.
TCD-5 describes specimen or container handling. This is not patient identity and not order identity; it is the physical or analyzer-side detail needed to move, test, store, or track the specimen correctly.
TCD-6 carries Automatic Repeat Allowed for this equipment or specimen workflow. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 0136; many real interfaces narrow that list further, so follow the receiver's implementation guide.
TCD-7 carries Reflex Allowed for this equipment or specimen workflow. Populate it only when the receiver has a clear use for it, and keep the value in the datatype shape shown in the generated field panel.
The generated panel links this to HL7 table 0136; many real interfaces narrow that list further, so follow the receiver's implementation guide.
TCD-8 tells the receiver the state of this equipment or specimen workflow. Status fields often drive workflow branches, so use the agreed code and do not infer a status just because another field looks complete.
The coded value should follow HL7 table 0389 or the narrower table in the local profile.
Related links
- SAC - Specimen Container detail
- SPM - Specimen
- OBR - Observation Request
- OBX - Observation/Result
- TCC - Test Code Configuration
- EQU - Equipment Detail
- ECD - Equipment Command
- ECR - Equipment Command Response
- OML_O21 - OML - Laboratory order
- OML_O33 - OML - Laboratory order for multiple orders related to a single specimen