HL7 OM2 Numeric Observation
HL7 field reference OM2 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 |
|---|---|---|---|---|---|
| OM2.1 | Sequence Number - Test/Observation Master File | No | No | NM | |
| OM2.2 | Units of Measure | No | No | CE | 9999 |
| OM2.3 | Range of Decimal Precision | No | Yes | NM | |
| OM2.4 | Corresponding SI Units of Measure | No | No | CE | 9999 |
| OM2.5 | SI Conversion Factor | No | No | TX | |
| OM2.6 | Reference (Normal) Range - Ordinal and Continuous Observations | No | Yes | RFR | |
| OM2.7 | Critical Range for Ordinal and Continuous Observations | No | Yes | RFR | |
| OM2.8 | Absolute Range for Ordinal and Continuous Observations | No | No | RFR | |
| OM2.9 | Delta Check Criteria | No | Yes | DLT | |
| OM2.10 | Minimum Meaningful Increments | No | No | NM |
OM2 adds numeric observation attributes such as ranges, units, precision, and expected values.
The standard describes OM2 this way: This segment contains the attributes of observations with continuous values (including those with data types of numeric, date, or time stamp). It can be applied to observation batteries of type A and C (see OM1-18 - Nature of Service/Test/Observation)
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 OM2 in MFN_M08 - Test/observation (numeric) master file and MFN_M11 - Test/calculated observations 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.
OM2-1 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.
OM2-2 supplies the units that make the companion numeric field meaningful. Units should be coded consistently, especially for medication, lab, specimen, and billing quantities.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM2-3 carries Range of Decimal Precision 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.
This field can repeat. Use repetitions for separate real-world values, not as a workaround for putting several unrelated ideas in one field.
OM2-4 supplies the units that make the companion numeric field meaningful. Units should be coded consistently, especially for medication, lab, specimen, and billing quantities.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM2-5 helps identify the product, software, device, or equipment involved. It is particularly useful when support needs to trace behaviour back to a specific build, lot, instrument, or manufacturer.
OM2-6 carries Reference (Normal) Range - Ordinal and Continuous Observations 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.
This field can repeat. Use repetitions for separate real-world values, not as a workaround for putting several unrelated ideas in one field.
OM2-7 carries Critical Range for Ordinal and Continuous Observations 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.
This field can repeat. Use repetitions for separate real-world values, not as a workaround for putting several unrelated ideas in one field.
OM2-8 carries Absolute Range for Ordinal and Continuous Observations 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.
OM2-9 carries Delta Check Criteria 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.
This field can repeat. Use repetitions for separate real-world values, not as a workaround for putting several unrelated ideas in one field.
OM2-10 carries Minimum Meaningful Increments 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.
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_M11 - Test/calculated observations master file