The EMA created a specification document
EU Individual Case Safety Report (ICSR)1 Implementation Guide
About the E2B (R3) data entry.
This document stipulates that at least one patient identifier is required to indicate that a patient exists, this is meet through the completion of at least one of the fields of the Patient characteristics tab. The use of “UNK”, “ASKU” or “NASK” nullflavors in any of the patient identifier fields does not indicate that a patient exists.