HL7 OM3 Categorical Service/Test/Observation
HL7 field reference OM3 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 |
|---|---|---|---|---|---|
| OM3.1 | Sequence Number - Test/Observation Master File | No | No | NM | |
| OM3.2 | Preferred Coding System | No | No | CE | 9999 |
| OM3.3 | Valid Coded "Answers" | No | No | CE | 9999 |
| OM3.4 | Normal Text/Codes for Categorical Observations | No | Yes | CE | 9999 |
| OM3.5 | Abnormal Text/Codes for Categorical Observations | No | Yes | CE | 9999 |
| OM3.6 | Critical Text/Codes for Categorical Observations | No | Yes | CE | 9999 |
| OM3.7 | Value Type | No | No | ID | 0125 |
OM3 adds categorical observation attributes and answer-set style configuration.
Master-file segments update reference data rather than describing a single patient event. They define locations, staff, providers, test catalogs, charge items, inventory items, languages, certificates, and other shared records.
Because many downstream messages depend on this data, small changes here can have large effects. Use stable identifiers, effective dates, action codes, and clear ownership rules instead of treating a master-file feed like a loose spreadsheet export.
The v2.5.1 structures show OM3 in MFN_M08 - Test/observation (numeric) master file and MFN_M09 - Test/observation (categorical) master file. 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.
OM3-1 identifies the Sequence Number - Test/Observation Master File for this master-file record. Send the identifier that the receiving system actually keys on, and keep the assigning authority or coding system visible when the datatype supports it.
OM3-2 carries Preferred Coding System for this master-file record. 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 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM3-3 carries Valid Coded "Answers" for this master-file record. 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 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM3-4 is human-readable context. Keep it useful for display and troubleshooting, but do not hide required workflow logic here unless the implementation guide explicitly says the receiver parses it.
Because the field can repeat, separate distinct statements into separate repetitions instead of creating one long hard-to-parse block.
OM3-5 is human-readable context. Keep it useful for display and troubleshooting, but do not hide required workflow logic here unless the implementation guide explicitly says the receiver parses it.
Because the field can repeat, separate distinct statements into separate repetitions instead of creating one long hard-to-parse block.
OM3-6 is human-readable context. Keep it useful for display and troubleshooting, but do not hide required workflow logic here unless the implementation guide explicitly says the receiver parses it.
Because the field can repeat, separate distinct statements into separate repetitions instead of creating one long hard-to-parse block.
OM3-7 qualifies the master-file record rather than identifying it. This is the sort of field receivers often use for branching, filtering, or display grouping.
Use the agreed value set, starting from HL7 table 0125. A local code without an agreed coding system is a small ambiguity that becomes a mapping problem later.
Related links
- MFI - Master File Identification
- MFE - Master File Entry
- MFA - Master File Acknowledgment
- LOC - Location Identification
- STF - Staff Identification
- PRA - Practitioner Detail
- OM1 - General Segment
- CDM - Charge Description Master
- MFN_M08 - Test/observation (numeric) master file
- MFN_M09 - Test/observation (categorical) master file