Union of http://hl7.org/fhir/ValueSet/observation-category and http://hl7.org/fhir/us/core/ValueSet/us-core-simple-observation-category

This is the ValueSet that contains all the codes in Observation Category Codes (http://hl7.org/fhir/ValueSet/observation-category) and US Core Simple Observation Category (http://hl7.org/fhir/us/core/ValueSet/us-core-simple-observation-category). E.g. what you have to deal with if you get resources containing codes in either of them

CodeSystem

Generated Narrative: ValueSet 354d8ed8-61db-4a4e-9cf1-f2745544108e-59

This value set includes codes based on the following rules: