A result observation must be represented with the observation. The value for "Observation / moodCode" in a result observation SHALL be EVN. A result observation SHALL contain at least one Observation / id. A result observation SHALL contain exactly one Observation / statusCode. A result observation SHALL contain exactly one Observation / code. A result observation SHALL contain exactly one Observation / value A result observation SHALL NOT contain Observation / referenceRange / observationRange / code, as this attribute is not used by the HL7 Clinical Statement or Lab Committee models. Where Observation / value is a physical quantity, the unit of measure SHALL be expressed using a valid UCUM expression. The value for “Observation / code” in a result observation SHOULD be selected from LOINC (codeSystem 2.16.840.1.113883.6.1) or SNOMED CT (codeSystem 2.16.840.1.113883.6.96). A result observation SHOULD contain exactly one Observation / effectiveTime, which represents the biologically relevant time (e.g. time the specimen was obtained from the patient). A result observation SHOULD contain exactly one Observation / interpretationCode. A result observation SHOULD contain one or more Observation / referenceRange to show the normal range of values for the observation result.