This value set includes codes based on the following rules:

• Include these codes as defined in http://terminology.hl7.org/CodeSystem/v3-NullFlavor version 2018-08-12

  Code	Display	Definition
  ASKU	asked but unknown	Information was sought but not found (e.g., patient was asked but didn't know)
  NA	not applicable	Known to have no proper value (e.g., last menstrual period for a male).
  NASK	not asked	This information has not been sought (e.g., patient was not asked)
  NAV	temporarily unavailable	Information is not available at this time but it is expected that it will be available later.
  NI	No Information	**Description:**The value is exceptional (missing, omitted, incomplete, improper). No information as to the reason for being an exceptional value is provided. This is the most general exceptional value. It is also the default exceptional value.
  NP	not present	Value is not present in a message. This is only defined in messages, never in application data! All values not present in the message must be replaced by the applicable default, or no-information (NI) as the default of all defaults.
  UNK	unknown	**Description:**A proper value is applicable, but not known. **Usage Notes**: This means the actual value is not known. If the only thing that is unknown is how to properly express the value in the necessary constraints (value set, datatype, etc.), then the OTH or UNC flavor should be used. No properties should be included for a datatype with this property unless: 1. Those properties themselves directly translate to a semantic of "unknown". (E.g. a local code sent as a translation that conveys 'unknown') 2. Those properties further qualify the nature of what is unknown. (E.g. specifying a use code of "H" and a URL prefix of "tel:" to convey that it is the home phone number that is unknown.)

• Include these codes as defined in http://terminology.hl7.org/CodeSystem/v2-0136 version 2.9

  Code	Display
  N	No
  Y	Yes

This value set expansion contains 9 concepts.