Searching WorldCat can be tricky. You can search by "subject" but if it is a long subject with many words and dates, sometimes you have to select "subject phrase."
The results don't divide down into categories like CONSORT or OhioLINK, but what it does do is divide results into tabs. Your best bet for finding primary sources is exploring the Archival or Internet tabs. However depending on your research, other tabs might also be helpful.