As shown with the core fields, the TEST_ID is the link between the 3 levels of data and the test background information table.
Some prior assessment of the assigned test identifiers has to be done in order to avoid duplicates.
In a running database the duplicate issues are easily resolved by adding a unique auto-generated key as the identifier between 3 levels of data and the test background information table.
Along with the TEST_ID it might be necessary to store the ID assigned to the sample at both the testing laboratory but also the centres laboratory in order to track the sample.