DiagnosticReport does not contain a core mechanism for indicating one report is an addendum of another. While we can mark a report with an amended or appended status, there is no core way of identifying which report it modifies.

There are extensions(DiagnosticReport Addendum Of, DiagnosticReport Extends, DiagnosticReport Replaces) which may or may not point in the wrong direction, but also it seems that but it seems that this should be a core functionality of the resource.

Alternatively, if we expect that an addendum is actually a modification of an existing report, without the need for a new report, then we should document this clearly in the resource narrative.

This issue is inspired by FHIR-26362.