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Table 3 Constraint on Observation.value when Observation.code is ASSERTION

From: Semantic validation of the use of SNOMED CT in HL7 clinical documents

Class Name

Observation

Class Code

OBS

Attribute Name

Observation.value

Narrative description

An act that is intended to result in new information about a subject. The main difference between observations and other acts is that it has a value attribute that is used to state the result of the assessment action described in Act.code.

Simple representation

((<<404684003| clinical finding|)OR(<<413350009| finding with explicit context|)OR (<<272379006| event|))

Notes

Where Observation.code = ASSERTION.

An alternative approach (now deprecated) is for the same value set to be communicated in Observation.code where the attribute Observation.value is not present in the Observation class instance.

As indicated in section 2.2.2.2 subheading 7, the situation may arise in which Observation.value is a SNOMED CT expression from the set specified in the 'simple representation' field of this table and Act.code is represented by a code other than ”ASSERTION”. For such an approach can only be safely used if interpretation of the Act.code together with the Observation.value does not yield a meaning that is substantially different from the meaning implied if the Act.code was ”ASSERTION”. Without exhaustive scrutiny of SNOMED CT's content it is not possible to identify that set of codes that can safely be used in this way in Act.code.