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Specimen Participation in Observations

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The HL7 participation type “specimen” relates an observation to the specimen on which an observation was made (or is to be made). The specimen participation allows type of specimen or an actual identifiable specimen to be specified.

Some SNOMED CT [ <<386053000 | evaluation procedure ] and [ <<363787002 | observable entity ] concepts indicate the type of specimen that is the subject of the measurement or observed property. Refinement is possible using the [ 116686009 | has specimen ] attribute to specify particular specimen types for any relevant procedure. Therefore, there is a potential overlap between two approaches to representation of the nature of the specimen.
  1. When using SNOMED CT to record an observation that applies to a specimen the nature of the specimen MAY be expressed separately using the Entity.code of the entity playing the role that is the target of the specimen participation
    • This type of representation may be appropriate in cases where it is also necessary to identify the specimen and where a single specimen is the subject of multiple different observations.
    • When using this form of representation:
      • The type of specimen SHOULD be expressed using an appropriate SNOMED CT concept in the Entity.code attribute.
      • If the SNOMED CT expression used in Observation.code specifies a value for the [ 116686009 | has specimen ] attribute, the value of this attribute SHALL be either the same as or less specific than the value used in the Entity.code.
  2. Alternatively, a specific SNOMED CT concept or expression MAY be used to specify the nature of the observation including the type of specimen.
    • This form MAY be appropriate to simple recording of result in a clinical record but does not allow the specific instance of the specimen to be identified.

The recommendations on representation of specimen take account of the current incomplete set of investigation codes available. Recent experience in the UK suggests that the first approach above, using the Entity.code is a more flexible basis for requesting and reporting laboratory investigation using SNOMED CT.

The guidance on use of SNOMED CT in the Entity.code attribute is intended to avoid conflicts or ambiguity that may result from representing the values of [ 116686009 | has specimen ] and Entity.code using different coding systems.