A rheumatoid factor (RF) test is a blood test that can help diagnose rheumatoid arthritis (RA). The test measures the amount of rheumatoid factor in your blood. Rheumatoid factor is an autoantibody ...

High concentrations of RF in the joints leads to the autoimmune disease rheumatoid arthritis (RA). An autoimmune disease is one in which the body attacks its own tissues. Rheumatoid factors are ...