Certain Study Attributes provide linkage to other aspects of the patient medical record. In particular, Patient ID links the study to the medical record, Study Date allows correlation to other patient medical events, and Accession Number links the Study to the relevant imaging order and study workflow. However, DICOM specifies these three critical Attributes as Type 2 in composite SOP Instances, and they might therefore be empty in Studies in the repository.

As a general quality assurance principle, but especially during migration, it is important that these Attributes have correct values. The Repository Query SOP Class and the Inventory IOD's Scope of Inventory allow Study selection using the extended (optional) capability "Empty Value Matching". If such matching is implemented in the repository system, it allows creation of an Inventory of Studies with empty Attributes. As a quality assurance process, such inventories may be produced on a regular basis, identified studies corrected as needed, and root causes for missing values identified and corrected as a process improvement task.