Definition of Rheumatoid Factor

Rheumatoid Factor, or RF as it is called, is a test designed to help diagnose two conditions: rheumatoid arthritis (RA) and Sjogren syndrome. It is typically ordered along with other autoimmune tests to help detect RA earlier. There can be more false-positive results as someone ages, so getting this test done when younger can be best.

The Rheumatoid Factor Test Order

If there are symptoms that include warmth, pain, stiffness, or swelling in the joints, this test may be ordered to test for rheumatoid arthritis (RA). It also can be used if there are swollen joint capsules or loss of bone evident on x-ray, or if there is nodules under the skin. If there is a negative test result and the symptoms continue, another RF test may be ordered. If there are symptoms including dry mouth, dry eyes, dry skin, joint pain, and muscle pain, the test may be ordered to check for Sjogren syndrome.

How the Rheumatoid Factor Test is Used

The RF test helps distinguishes RA and Sjogren syndrome from other forms of arthritis. It may be ordered along with other diagnostic tests to help detect RA. Tests that may be ordered with it to help diagnose Sjogren syndrome include the anti-SS-A and anti-SS-B tests.

Rheumatoid Factor Test Results

The test is interpreted with the history and the symptoms presented by the patient. If there is a negative test result it still will not rule out the condition, as 20 percent of those with RA will have a negative test result. Positive test results are also seen in those that are healthy, or those with other conditions such as syphilis, lupus, tuberculosis, cancer, or endocarditis.