Maximum Length: Varies - dependent on length of longest code in code set.
The value of such a field follows the formatting rules for an ST field except that it is drawn from a table of legal values. There shall be an HL7 table number associated with ID data types. An example of an ID field is OBR-25-result status. This data type should be used only for HL7 tables (see Section 2.5.3.6 -Table). The reverse is not true, since in some circumstances it is more appropriate to use the CNE or CWE data type for HL7 tables.
1Descriptionidentifier → Coded Value for HL7-Defined Tables
Primitive Type
This is a primitive data type with no internal structure. It represents a single value.