Sorry so long in reply.
Blood work, that I can remember...
CBC, CRP, Sed rate, AnA, antibodies testing, thyroid function, RA factor, some sort of genetic testing for hereditary markers associated with auto-immune disorders, maybe liver & kidney function. There's probably more but you only have to be stuck once then it may be weeks before you get results, a dx & some kind of meds/treatment program.
This was my experience anyway, hope it helped.
May relief come your way.