I know what it is, fundamentally, but not how to make it with the tools in Thedas. But the result is pretty obvious, at least with the kind of testing I'm talking about. The sample clumps in a way you can see if the antigen you're testing for is present.

But hey, look, we don't expect you to crack blood transfusions yourself. I don't expect to crack it. As you're saying, it's the kind of thing that's worth spreading to our allies so they can work on it. Huge public health benefits, down the road if not in the short term. Whatever native scientist works it out here can take credit [somewhere, the entire Diplomacy division may have just gotten a headache], as long as it saves lives. It's the exact right kind of thing for you to be looking at.