OBX — Observation / Result
HL7 v2.5.1 Observation / Result segment reference
A single result value. Multiple OBX segments follow each OBR to report individual result components.
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The table below lists the commonly used fields of the OBX (Observation / Result) segment. Field positions follow the HL7 v2.5.1 specification.
| Field | Name | Type | Len | Use | Description |
|---|---|---|---|---|---|
| OBX-1 | Set ID | SI | 4 | R | Sequence number starting at 1 within the parent OBR.e.g. 1 |
| OBX-2 | Value Type | ID | 3 | C | Data type of the result: NM (numeric), ST (string), CE (coded), TX (text), DT (date), TS (timestamp).e.g. NM HL7 table 0125 |
| OBX-3 | Observation Identifier | CE | 250 | R | What is being measured. Typically LOINC. Format: code^description^system.e.g. 2345-7^Glucose^LN |
| OBX-5 | Observation Value | Varies | 65536 | C | The actual result value. Type matches OBX.2.e.g. 95 |
| OBX-6 | Units | CE | 250 | O | Units of measure for numeric results.e.g. mg/dL |
| OBX-7 | Reference Range | ST | 60 | O | Normal range for this test. Format varies: "low-high", "<high", ">low".e.g. 74-106 |
| OBX-8 | Abnormal Flags | IS | 5 | O | N=normal, L=low, H=high, LL=critical low, HH=critical high, A=abnormal.e.g. N HL7 table 0078 |
| OBX-11 | Observation Result Status | ID | 1 | R | F=final, P=preliminary, C=corrected, X=cancelled, D=deleted.e.g. F HL7 table 0085 |
| OBX-14 | Date/Time of Observation | TS | 26 | O | When this specific result was observed.e.g. 20240315110000 |
Use column: R Required · C Conditional · O Optional. Type column uses HL7 data-type codes (ST = string, NM = numeric, TS = timestamp, CX = extended composite ID, XPN = extended person name, and so on).