The immune system usually produces antibodies to fight diseases. In rheumatoid arthritis (RA), however, an antibody is present in the blood that is not beneficial to the patient. This antibody is called the rheumatoid arthritis factor or simply, rheumatoid factor (RF). Physicians commonly order a blood test to detect and measure rheumatoid arthritis factor in patients showing symptoms of RA.
RA is an autoimmune disease that causes long-term inflammation of several joints in the body. The joints frequently affected are the joints of the knees, wrists, ankles, and fingers. Symptoms usually experienced by patients include redness and swelling of the affected joints, weakness, and morning stiffness. Joint pain is often bilateral, which means that pain is often felt at the same time in both knees or wrist.
There are other disorders where the level of rheumatoid arthritis factor is also increased. These include Sjogren syndrome, scleroderma, and Raynaud's phenomenon. Sjogren syndrome is a condition in which the tear glands or the salivary glands are damaged. Affected patients usually complain of dry eyes or dry mouth, respectively.
Scleroderma affects the connective tissues and causes hard, thick skin and tissue damage. Patients with Raynaud's phenomenon experience paleness and bluish discoloration of the skin when exposed to cold. Infectious diseases such as tuberculosis, hepatitis C, and syphilis may also accompany high RF levels in the blood. Rheumatoid arthritis factor may also be detected in a few healthy individuals who have a history of RA in the family.
A rheumatoid arthritis factor blood test is usually done by taking a blood sample from the patient's vein. The blood sample is then processed in the laboratory and the amount of RF is measured. No preparation is usually needed for the test. A slight degree of pain or stinging sensation may sometimes be felt during the blood extraction procedure.
Other tests may also be ordered together with the rheumatoid arthritis factor test. These include a complete blood count (CBC), an erythrocyte sedimentation rate (ESR), and a C-reactive protein (CRP), among other tests. Results form such tests are often considered along with the patient's symptoms, past medical records, and family history before a definite diagnosis of RA or other disorder is given.
About 80 percent of RA patients have elevated levels of rheumatoid arthritis factor. Patients with very elevated levels of rheumatoid arthritis factor may present with more severe symptoms of RA. Some may develop rheumatoid lung disease and rheumatoid nodules.
