HL7 OML^O21 (Laboratory Order Message)
OML^O21 is the HL7v2 laboratory order message message, defined in HL7v2 from v2.4 through v2.8.2. Its v2.8.2 structure carries 73 segments and groups, 21 of them required.
Full message structure (v2.8.2)
Every segment and group the standard defines for OML^O21, in order, straight from the machine-readable specification. Indented rows sit inside the repeating group above them. R is required, O optional, C conditional; ∞ means the group or segment may repeat without a defined limit.
| Segment / group | Usage | Repeats |
|---|---|---|
| MSH | R | 1 |
| SFT | O | ∞ |
| UAC | O | 1 |
| NTE | O | ∞ |
| PATIENT (group) | O | 1 |
| PID | R | 1 |
| PD1 | O | 1 |
| PRT | O | ∞ |
| NTE | O | ∞ |
| NK1 | O | ∞ |
| PATIENT_VISIT (group) | O | 1 |
| PV1 | R | 1 |
| PV2 | O | 1 |
| PRT | O | ∞ |
| INSURANCE (group) | O | ∞ |
| IN1 | R | 1 |
| IN2 | O | 1 |
| IN3 | O | 1 |
| GT1 | O | 1 |
| AL1 | O | ∞ |
| ORDER (group) | R | ∞ |
| ORC | R | 1 |
| PRT | O | ∞ |
| TIMING (group) | O | ∞ |
| TQ1 | R | 1 |
| TQ2 | O | ∞ |
| OBSERVATION_REQUEST (group) | O | 1 |
| OBR | R | 1 |
| TCD | O | 1 |
| NTE | O | ∞ |
| PRT | O | ∞ |
| CTD | O | 1 |
| DG1 | O | ∞ |
| OBSERVATION (group) | O | ∞ |
| OBX | R | 1 |
| PRT | O | ∞ |
| TCD | O | 1 |
| NTE | O | ∞ |
| SPECIMEN (group) | O | ∞ |
| SPM | R | 1 |
| SPECIMEN_OBSERVATION (group) | O | ∞ |
| OBX | R | 1 |
| PRT | O | ∞ |
| CONTAINER (group) | O | ∞ |
| SAC | R | 1 |
| CONTAINER_OBSERVATION (group) | O | ∞ |
| OBX | R | 1 |
| PRT | O | ∞ |
| PRIOR_RESULT (group) | O | ∞ |
| PATIENT_PRIOR (group) | O | 1 |
| PID | R | 1 |
| PD1 | O | 1 |
| PRT | O | ∞ |
| PATIENT_VISIT_PRIOR (group) | O | 1 |
| PV1 | R | 1 |
| PV2 | O | 1 |
| PRT | O | ∞ |
| AL1 | O | ∞ |
| ORDER_PRIOR (group) | R | ∞ |
| ORC | R | 1 |
| OBR | R | 1 |
| NTE | O | ∞ |
| PRT | O | ∞ |
| TIMING_PRIOR (group) | O | ∞ |
| TQ1 | R | 1 |
| TQ2 | O | ∞ |
| OBSERVATION_PRIOR (group) | R | ∞ |
| OBX | R | 1 |
| PRT | O | ∞ |
| NTE | O | ∞ |
| FT1 | O | ∞ |
| CTI | O | ∞ |
| BLG | O | 1 |
Which HL7v2 versions changed OML^O21?
OML^O21 has been defined since v2.4. Consecutive versions sharing an identical structure are grouped, so a single row spanning several versions means nothing changed across them.
| Versions | What changed |
|---|---|
| v2.4 | First defined, with 51 segments and groups. |
| v2.5 - v2.5.1 | Added CTD, NK1, SFT, SPM, TQ1, TQ2. |
| v2.6 | Same segments, but usage or repeat counts changed. |
| v2.7 - v2.8.2 | Added PRT, UAC. |