Could you please help me clarify the following point?
According to the SNOMED CT Starter Guide, it is stated that:
“Qualifier value represents the values for some SNOMED CT attributes, where those values are not subtypes of other top level concepts (e.g., |left|, |abnormal result|, |severe|).”
This suggests that Qualifier values are intended to be used as attribute values within expressions, and not as standalone clinical concepts.
Therefore, only concepts that fall within the appropriate domain category may be used as focus concepts – is that correct?
Based on this, and considering the MRCM (Machine Readable Concept Model) rules, I understand that the concept:
397669002 |Age (qualifier value)|
should not be used as a focus concept.
In contrast, the concept: 424144002 |Current chronological age (observable entity)|
belongs to an appropriate domain and can be used as a focus concept, for example, in an Observation.
Is this interpretation correct according to SNOMED CT modeling principles?
Yes, you are absolutely correct. Qualifier concepts can not be used as a focus concept, they can only be used as the value of specific attributes.
The MRCM Browser may also be useful when selecting a focus concept. The domains of SNOMED CT are listed on the left column. Once selected the relevant attributes are displayed in the central column. Finally the right hand column shows the range constraint for any selected attribute.
You should see Qualifier values mentioned in the Attribute Range Constraint when an applicable attribute is selected. For example within the “Observable entity” domain when “Has realization” is selected you will see “<< 719982003 |Process (qualifier value)|” within the Range Constraint meaning that “719982003 |Process (qualifier value)|” or any of it’s subtypes can be used as the value. There is also a search box nearer the bottom of the Attribute Range column that can be used to ensure specific qualifiers and other values are permitted in the selected attribute.