Concept Code	Concept Name	Preferred Concept Name	Code System
	as-text	As Text	The content of the data is represented in the resource narrative.	Data Absent Reason	Details
	asked-declined	Asked But Declined	The source was asked but declined to answer.	Data Absent Reason	Details
	asked-unknown	Asked But Unknown	The source was asked but does not know the value.	Data Absent Reason	Details
	error	Error	Some system or workflow process error means that the information is not available.	Data Absent Reason	Details
	masked	Masked	The information is not available due to security, privacy or related reasons.	Data Absent Reason	Details
	negative-infinity	Negative Infinity (NINF)	The numeric value is excessively low and unrepresentable due to a floating point processing error.	Data Absent Reason	Details
	not-a-number	Not a Number (NaN)	The numeric value is undefined or unrepresentable due to a floating point processing error.	Data Absent Reason	Details
	not-applicable	Not Applicable	There is no proper value for this element (e.g. last menstrual period for a male).	Data Absent Reason	Details
	not-asked	Not Asked	The workflow didn't lead to this value being known.	Data Absent Reason	Details
	not-performed	Not Performed	The value is not available because the observation procedure (test, etc.) was not performed.	Data Absent Reason	Details
	not-permitted	Not Permitted	The value is not permitted in this context (e.g. due to profiles, or the base data types).	Data Absent Reason	Details
	positive-infinity	Positive Infinity (PINF)	The numeric value is excessively high and unrepresentable due to a floating point processing error.	Data Absent Reason	Details
	temp-unknown	Temporarily Unknown	There is reason to expect (from the workflow) that the value may become known.	Data Absent Reason	Details
	unknown	Unknown	The value is expected to exist but is not known.	Data Absent Reason	Details
	unsupported	Unsupported	The source system wasn't capable of supporting this element.	Data Absent Reason	Details