Rheumatoid Factor (RF) Test in Malcha Marg, Delhi

Rheumatoid factor (RF) is an antibody that can attack the body's own antibodies. It was the first blood test used to help diagnose rheumatoid arthritis (RA), an autoimmune disease where the joint lining becomes inflamed, causing painful, swollen, stiff joints, often in the hands and feet on both sides of the body.

RF is found in about 70–80% of people with established RA, but it is not specific. It can also be positive in Sjögren's syndrome, lupus, chronic infections such as hepatitis C and TB, liver disease, and in a small number of healthy people, especially older adults. About a quarter of RA patients are RF-negative ("seronegative").

For these reasons RF is interpreted along with symptoms, a physical exam, ESR/CRP and, importantly, anti-CCP antibodies, which are more specific for RA. A high RF together with positive anti-CCP suggests more aggressive disease and a higher risk of joint damage.

Rheumatoid arthritis: early diagnosis matters

Treatment started within the first few months of symptoms prevents much joint damage. Early signs include morning stiffness lasting over an hour, swelling of the small joints of the hands (knuckles and wrist) and feet on both sides, and tiredness. Doctors use symptoms, examination, RF, anti-CCP, ESR, CRP and sometimes ultrasound or X-rays to decide.

Prognosis and treatment

High RF and anti-CCP together predict more severe disease. Treatment uses disease-modifying drugs such as methotrexate, along with physiotherapy and lifestyle measures, under a rheumatologist's care. Many people achieve remission with timely treatment.

Other reasons for a positive RF

RF can be positive in hepatitis C, TB, endocarditis, lung disease and, in a small share of healthy older adults. For this reason, a positive RF without joint symptoms usually needs no treatment.