HL7 OM4 Observations that Require Specimens
HL7 field reference OM4 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 |
|---|---|---|---|---|---|
| OM4.1 | Sequence Number - Test/Observation Master File | No | No | NM | |
| OM4.2 | Derived Specimen | No | No | ID | 0170 |
| OM4.3 | Container Description | No | No | TX | 0170 |
| OM4.4 | Container Volume | No | No | NM | |
| OM4.5 | Container Units | No | No | CE | 9999 |
| OM4.6 | Specimen | No | No | CE | 9999 |
| OM4.7 | Additive | No | No | CWE | 0371 |
| OM4.8 | Preparation | No | No | TX | |
| OM4.9 | Special Handling Requirements | No | No | TX | |
| OM4.10 | Normal Collection Volume | No | No | CQ | |
| OM4.11 | Minimum Collection Volume | No | No | CQ | |
| OM4.12 | Specimen Requirements | No | No | TX | |
| OM4.13 | Specimen Priorities | No | Yes | ID | 0027 |
| OM4.14 | Specimen Retention Time | No | No | CQ | 0027 |
OM4 describes specimen requirements for observations and services.
The standard describes OM4 this way: This segment applies to observations/batteries that require a specimen for their performance. When an observation or battery requires multiple specimens for their performance (e.g., creatinine clearance requires a 24-hour urine specimen and a serum specimen), multiple segments may be included, one for each specimen type.
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 OM4 in MFN_M08 - Test/observation (numeric) master file, MFN_M09 - Test/observation (categorical) master file, and MFN_M10 - Test /observation batteries 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.
OM4-1 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.
OM4-2 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.
The generated panel links this to HL7 table 0170; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM4-3 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.
The generated panel links this to HL7 table 0170; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM4-4 carries a measured, counted, priced, or dosed value. A number without the expected unit, currency, or companion qualifier is much easier to misread than an empty field.
OM4-5 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.
OM4-6 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.
The generated panel links this to HL7 table 9999; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM4-7 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.
The generated panel links this to HL7 table 0371; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM4-8 carries Preparation 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.
OM4-9 carries Special Handling Requirements 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.
OM4-10 carries a measured, counted, priced, or dosed value. A number without the expected unit, currency, or companion qualifier is much easier to misread than an empty field.
OM4-11 carries a measured, counted, priced, or dosed value. A number without the expected unit, currency, or companion qualifier is much easier to misread than an empty field.
OM4-12 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.
OM4-13 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.
The generated panel links this to HL7 table 0027; many real interfaces narrow that list further, so follow the receiver's implementation guide.
OM4-14 is a timing field. Send the real source-system precision, do not pad unknown dates or times, and agree how timezone offsets are handled when time of day matters.
The generated panel links this to HL7 table 0027; many real interfaces narrow that list further, so follow the receiver's implementation guide.
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