The rheumatoid factor (RF) is used to help diagnose rheumatoid arthritis (RA) and to distinguish it from other types of arthritis that cause have similar symptoms of joint pain, inflammation, and stiffness. It is often combined with other tests like antinuclear antibody (ANA) and other markers of inflammation (C-reactive protein and ESR). The test is not diagnostic or specific and must be interpreted in the light of the patient’s clinical profile. In individuals who have symptoms and signs of RA, high levels of RF indicate that it is likely that they have RA. A negative RF test does not rule out the disease as ~20% of patients may test negative for it or may have very low levels. A positive RF test can be seen in healthy individuals and in conditions like viral infection, collagen diseases like SLE, sarcoidosis, tuberculosis, syphilis etc.