Great questions and complicated. Yes, the positive rheumatoid factor could be from hepatitis C but usually it is positive with hep C when you have arthritis and something called vasculitis. Doesn’t sound like the case for you. The positive RF could also represent pre-clinical RA. In other words, the blood test (RF) can be positive for years before the joint pain develops. One other test that can help is the anti-CCP antibody test. If that is positive, that makes the diagnosis of RA much more likely — meaning that the patient, even if aymptomatic now, is likely to develop it down the road. The anti-CCP test is usually negative in hepatitis C.