This page is part of the FHIR Specification (v1.8.0: STU 3 Draft). The current version which supercedes this version is 5.0.0.  For a full list of available versions, see the Directory of published versions 
. Page versions: R3 R2
This is a value set defined by the FHIR project.
Summary
| Defining URL: | http://hl7.org/fhir/ValueSet/observation-valueabsentreason | 
| Name: | Observation Value Absent Reason | 
| Definition: | This value set defines the set of codes for identifying the reason why the expected result in Observation.value[x] is missing. | 
| Committee: | Orders and Observations   Work Group | 
| OID: | 2.16.840.1.113883.4.642.2.221 (for OID based terminology systems) | 
| Source Resource | XML / JSON | 
This value set is used in the following places:
This value set includes codes from the following code systems:
This expansion generated 06 Dec 2016
This value set contains 10 concepts
Expansion based on http://hl7.org/fhir/data-absent-reason version 1.8.0
All codes from system http://hl7.org/fhir/data-absent-reason
| Code | Display | Definition | 
| unknown | Unknown | The value is not known. | 
| asked | Asked | The source human does not know the value. | 
| temp | Temp | There is reason to expect (from the workflow) that the value may become known. | 
| not-asked | Not Asked | The workflow didn't lead to this value being known. | 
| masked | Masked | The information is not available due to security, privacy or related reasons. | 
| unsupported | Unsupported | The source system wasn't capable of supporting this element. | 
| astext | As Text | The content of the data is represented in the resource narrative. | 
| error | Error | Some system or workflow process error means that the information is not available. | 
| NaN | Not a Number | NaN, standing for not a number, is a numeric data type value representing an undefined or unrepresentable value. | 
| not-performed | Not Performed | The value is not available because the observation procedure (test, etc.) was not performed. | 
See the full registry of value sets defined as part of FHIR.
Explanation of the columns that may appear on this page:
| Level | A few code lists that FHIR defines are hierarchical - each code is assigned a level. In this scheme, some codes are under other codes, and imply that the code they are under also applies | 
| Source | The source of the definition of the code (when the value set draws in codes defined elsewhere) | 
| Code | The code (used as the code in the resource instance) | 
| Display | The display (used in the display element of a Coding). If there is no display, implementers should not simply display the code, but map the concept into their application | 
| Definition | An explanation of the meaning of the concept | 
| Comments | Additional notes about how to use the code |