HL7 OM6 Observations that are Calculated from Other Observations
HL7 field reference OM6 fields from HL7 v2.5.1 Show fields
OM6 describes observations calculated from other observations.
The standard describes OM6 this way: This segment contains the information about quantities that are derived from one or more other quantities or direct observations by mathematical or logical means.
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 OM6 in 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.
OM6-1 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.
OM6-2 carries Derivation Rule 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.