What is the Rheumatoid Factor?

Rheumatoid factor refers to an antibody that may be present in the blood of individuals diagnosed with rheumatoid arthritis. Typically, rheumatoid factor is not generally present in the bloodstreams of the majority of the population. Sometimes, however, it may be detected in a small portion of healthy people. In addition, an elevated rheumatoid factor may be present in individuals over the age of 65. A simple blood test can detect it, and no special preparation is needed prior to testing.

Generally, although rheumatoid arthritis is the most common medical condition associated with an elevated rheumatoid factor, other conditions can elicit a positive test as well. Typically, autoimmune diseases, such as Sjogren's syndrome, scleroderma, and systemic lupus erythematosus can return a positive rheumatoid factor. Similarly, infections can also play a role in the positive rheumatoid factor. Occasionally, patients diagnosed with tuberculosis, bacterial endocarditis or osteomyelitis may have a positive test.

Typically, the amount or presence of rheumatoid factor is generally measured by a procedure known as agglutination testing. In this procedure, small beads covered with antibodies are combined with the patient's blood. If rheumatoid factor is present in the blood, the beads will agglutinate, or clump together. Another method is called the nephelometry test. This procedure combines the patient's blood with antibodies that promote blood clotting in the presence of a positive factor.

Diagnosing rheumatoid arthritis using this blood test is only one component in making a positive diagnosis. The physician generally will only make the diagnosis of rheumatoid arthritis when both a positive blood test is present and when symptoms are present. Common symptoms of rheumatoid arthritis include pain, swelling and morning stiffness in one or multiple joints. Frequently, x-rays of the affected joints will demonstrate inflamed joint capsules and bone and cartilage loss as well.

In addition to the rheumatoid antibody test to detect the presence of rheumatoid arthritis, other blood tests are often utilized to substantiate the diagnosis. A diagnostic blood test called an erythrocyte sedimentation rate, or ESR is a test that if elevated, may indicate medical conditions associated with inflammation in the body. Most often, the rheumatoid arthritis patient will have an elevated ESR because rheumatoid arthritis involves the inflammatory process.

It is important to note, that the rheumatoid antibody factor test is neither specific nor diagnostic. Generally, it usually is only found diagnostic when other factors are present. Other factors that need to be present in conjunction with the antibody blood test are the patient's symptoms and his medical history. Many times, when a positive test result is reported, the physician may order a repeat test in the event of predisposing factors, such as lab error or presence of infection.