This is the ValueSet that contains all the codes in Test Usage Terminology (http://hl7.org/fhir/us/pq-cmc-fda/ValueSet/pqcmc-test-usage-terminology) and Test Usage Terminology (http://hl7.org/fhir/us/pq-cmc-fda/ValueSet/pqcmc-test-usage-terminology). E.g. what you have to deal with if you get resources containing codes in either of them