Can't get guaranteed diagnostic on kids

I don't think the intention is for players to seek out guaranteed diagnoses all of the time. They're useful at the beginning of the career when you're learning the symptoms of each disease but by level 9 you really shouldn't need them. The idea at that point is more to run just a few tests to narrow down the choices a little bit, and then use past experience with the symptoms to pick the correct diagnosis.

You can still get that guaranteed diagnosis sometimes also on a child.


Sometimes though as @Cupid says you just have to make a decision. Using the symptoms you see or don't see helps. Picking a patient to work on helps me. I try to pick one with evident symptoms. It makes it more fun for me that way also.
On this patient in the picture I pretty much had to do everything nearly a full exam, swab and x-ray. The dx finally popped up when analysing the swab sample.

just do two xrays and go through all the examinations plus test a sample and you should get a guarantee.