A rheumatoid factor (RF) test detects rheumatoid factor, a type of antibody (proteins that fight off harmful substances) in your blood. RF antibodies sometimes attack healthy cells and tissues, ...
What Is the Rheumatoid Factor Test? A rheumatoid factor test, or RF test, is a blood test to look for rheumatoid factors in your blood. High levels of rheumatoid factor can show up in people with ...