ObservationRelationshipType

This code system http://hl7.org/fhir/observation-relationshiptypes defines the following codes:

Code	Display	Definition
has-member	Has Member	This observation is a group observation (e.g. a battery, a panel of tests, a set of vital sign measurements) that includes the target as a member of the group.
derived-from	Derived From	The target resource (Observation or QuestionnaireResponse) is part of the information from which this observation value is derived. (e.g. calculated anion gap, Apgar score) NOTE: "derived-from" is the only logical choice when referencing QuestionnaireResponse.
sequel-to	Sequel To	This observation follows the target observation (e.g. timed tests such as Glucose Tolerance Test).
replaces	Replaces	This observation replaces a previous observation (i.e. a revised value). The target observation is now obsolete.
qualified-by	Qualified By	The value of the target observation qualifies (refines) the semantics of the source observation (e.g. a lipemia measure target from a plasma measure).
interfered-by	Interfered By	The value of the target observation interferes (degrades quality, or prevents valid observation) with the semantics of the source observation (e.g. a hemolysis measure target from a plasma potassium measure, which has no value).