She probably was testing your blood for presence of alleles (different forms) of the Human leukocyte antigen (HLA) group of proteins. These are proteins that are heavily involved in the function of your immune system, and so the presence/absence of different forms can be used to flag up your susceptibility to various autoimmune conditions (those where your immune mistakenly attacks your body). It's likely she identified something like HLA-DR4, which is a variant that's associated with increased rheumatoid arthritis and various other conditions, so she sent you to a rheumatologist, as the positive result for HLA-DR4 makes it more likely that there could be rheumatism involved, so you need to get it checked out. Note, however, that increased susceptibility doesn't necessarily mean you have something - I have some of the HLA alleles associated with arthritis, but have yet to exhibit any symptoms, and probably won't until I'm much older. Hopefully that helps a little, although check with the doctors as I may be off the mark - this isn't medical advice. And good luck with your follow-up appointments!