Typically, patient identification Keyword Types should not be used in Multi-Instance Keyword Type Groups. However, if your system includes the MRN, Master Patient Index, or Chart ID Keyword Type in a Multi-Instance Keyword Type Group, then you must add the assigning authority Keyword Type to that Multi-Instance Keyword Type Group.
This way, if a document is indexed with multiple values for an identifier, each identifier will be grouped with its corresponding assigning authority.