Testing for crazy stuff

My old doctor diagnosed me with lupus and told me that he wouldn't give me any of the pills because they would kill me so I got a new doctor she is sending me in for a syphilis test and an HIV test which I do not understand
Says their test that will help her figure out if I really have lupus I read about it and it says it will give me a false positive result and then she would have to prove it was lupus and not syphilis or HIV. To much for me should I change drs