Source:http://linkedlifedata.com/resource/umls/id/C0443354
HL7V3.0: <p>The target of an Observation action. Links an observation to a Role whose player is the substance or most specific component entity (material, micro-organism, etc.) being measured within the subject.</p><p><i>Examples:</i>A "plasma porcelain substance concentration" has analyte a Role with player substance Entity "porcelain".</p><p><i>UsageNotes:</i>The Role that this participation connects to may be any Role whose player is that substance measured. Very often, the scoper may indicate the system in which the component is being measured. E.g., for "plasma porcelain" the scoper could be "Plasma".</p>