Question, would an administrative gender change result in NHS No being superseded or would the existing NHS No be retained ?
A change in administrative gender would not necessarily result in the PDS record (and thus its NHS number) being superseded.
For example, if a PATCH request is sent to PDS FHIR API with an update to the gender field, the record and its NHS number remain otherwise unchanged.
That being said, when a patient goes through gender reassignment, a new PDS record (and thus new NHS number) are created - see Adoption and gender reassignment processes