OBX — Observation/Result
Appears after OBR in ORU (result) messages and in ORM (orders) when current observations are sent with an order. Multiple OBX segments are grouped under a single OBR.
The OBX segment carries a single observation value or result. Multiple OBX segments appear in a message for multi-analyte test results. It supports a wide variety of value types from numeric lab values to coded findings to document references.
Real-World Context
OBX is where the clinical data lives. OBX.2 (value type) and OBX.5 (observation value) are the most critical fields — if the value type does not match the actual data format in OBX.5, the receiving system cannot parse the result. The abnormal flag in OBX.8 drives clinical alerting — missing H/L/AA/LL/HH flags are the top reason critical value alerts fail to fire.
Field Reference
Click any row to see the full description, common values, and troubleshooting tip.
| # | Field Name | Type | Req | Max Len | |
|---|---|---|---|---|---|
| 1 | Set ID - OBX | SI | O | 4 | ▶ |
| 2 | Value Type | ID | R | 2 | ▶ |
| 3 | Observation Identifier | CE | R | 250 | ▶ |
| 4 | Observation Sub-ID | ST | O | 20 | ▶ |
| 5 | Observation Value | Varies | O | 65536 | ▶ |
| 6 | Units | CE | O | 250 | ▶ |
| 7 | Reference Range | ST | O | 60 | ▶ |
| 8 | Interpretation Codes | IS | O | 5 | ▶ |
| 9 | Probability | NM | O | 5 | ▶ |
| 10 | Nature of Abnormal Test | ID | O | 2 | ▶ |
| 11 | Observation Result Status | ID | R | 1 | ▶ |
| 12 | Effective Date of Reference Range | TS | O | 26 | ▶ |
| 13 | User Defined Access Checks | ST | O | 20 | ▶ |
| 14 | Observation Date/Time | TS | O | 26 | ▶ |
| 15 | Producer ID | CE | O | 250 | ▶ |
| 16 | Responsible Observer | XCN | O | 250 | ▶ |
| 17 | Observation Method | CE | O | 250 | ▶ |
| 18 | Equipment Instance Identifier | EI | O | 427 | ▶ |
| 19 | Date/Time of Analysis | TS | O | 26 | ▶ |
| 20 | Reserved for Harmonization with V2.6 (20-23) | ST | O | 0 | ▶ |
| 24 | Performing Organization Name | XON | O | 567 | ▶ |
| 25 | Performing Organization Address | XAD | O | 631 | ▶ |
Example Segment
1OBX||1|NM|718-7^Hemoglobin [Mass/vol] in Blood^LN||14.2|g/dL^grams per deciliter^UCUM|12.0-17.5|N|||F|||20260310162000||LAB_MAIN^Main Laboratory^LOCAL|1234567890^JONES^ROBERT^^^MD^NPI|HPLC^HPLC method|COBAS_6800^MAIN_LAB
Related Segments
Used In Message Types
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