Event identifier

Definition: This field contains the HL7 event identifier corresponding to the original trigger event. Its contents dictate the format of the response message. Hence, a value of "A04" in this field indicates a request for the data associated with the "register a patient" trigger event. The ERP response message returns the contents of the "register a patient" message defined in Chapter 3. If more than one match is found, the ERP returns repeating groups of the segments defined by the "A04" message.