| Lvl | Code | Display | Definition | 
| 1 | 
unknown  | 
Unknown | 
The value is expected to exist but is not known. | 
| 2 | 
  asked-unknown  | 
Asked But Unknown | 
The source was asked but does not know the value. | 
| 2 | 
  temp-unknown  | 
Temporarily Unknown | 
There is reason to expect (from the workflow) that the value may become known. | 
| 2 | 
  not-asked  | 
Not Asked | 
The workflow didn't lead to this value being known. | 
| 2 | 
  asked-declined  | 
Asked But Declined | 
The source was asked but declined to answer. | 
| 1 | 
masked  | 
Masked | 
The information is not available due to security, privacy or related reasons. | 
| 1 | 
not-applicable  | 
Not Applicable | 
There is no proper value for this element (e.g. last menstrual period for a male). | 
| 1 | 
unsupported  | 
Unsupported | 
The source system wasn't capable of supporting this element. | 
| 1 | 
as-text  | 
As Text | 
The content of the data is represented in the resource narrative. | 
| 1 | 
error  | 
Error | 
Some system or workflow process error means that the information is not available. | 
| 2 | 
  not-a-number  | 
Not a Number (NaN) | 
The numeric value is undefined or unrepresentable due to a floating point processing error. | 
| 2 | 
  negative-infinity  | 
Negative Infinity (NINF) | 
The numeric value is excessively low and unrepresentable due to a floating point processing        error. | 
| 2 | 
  positive-infinity  | 
Positive Infinity (PINF) | 
The numeric value is excessively high and unrepresentable due to a floating point processing        error. | 
| 1 | 
not-performed  | 
Not Performed | 
The value is not available because the observation procedure (test, etc.) was not performed. | 
| 1 | 
not-permitted  | 
Not Permitted | 
The value is not permitted in this context (e.g. due to profiles, or the base data types). |