Synonyms

   RA Quantitative

Clinical Significance

   The purpose of testing for rheumatoid factor is to determine if a patient has RF in their blood. While some healthy people have detectable RF, a positive result on an RF test can also indicate an underlying health condition and may warrant additional diagnostic testing in patients with other signs or symptoms of an autoimmune disorder. An RF test can help doctors diagnose autoimmune disorders and estimate disease severity:

   Diagnosing autoimmune disorders: Diagnostic testing may be appropriate for patients with symptoms of rheumatoid arthritis, Sjögren’s syndrome, or another autoimmune disorder. For example, a patient’s doctor may recommend a test for rheumatoid factor if a patient is experiencing pain and inflammation in multiple joints that isn’t due to another condition.

   Estimating disease severity: Rheumatoid factor testing can also provide doctors with information about the severity of rheumatoid arthritis. Patients with higher levels of RF are more likely to have severe rheumatoid arthritis, as well as disease that affects parts of the body outside of the joints, such as the lungs and blood vessels.

Specimen

   Serum

Stability

   Refrigerated (preferred) : 14 days

   Frozen : 14 days

Reference Range

   0 – 20 IU/ml

Interpretation

   A negative test result indicates that little to no RF was found in the blood, but this does not always rule out an underlying health issue. Up to 20% of people with rheumatoid arthritis may have a negative RF test result, and their result may change over time.

   Testing positive for rheumatoid factor may indicate an underlying health condition but is insufficient to diagnose a condition on its own. Around 5 to 10% of healthy people have RF detected in their blood. Positive results may also be related to an underlying autoimmune disorder, certain infections, and some types of cancer.

   While high levels alone cannot diagnose any condition, research suggests that the higher the amount of RF in the blood, the greater the likelihood that a patient has an autoimmune disorder. In order to diagnose the cause of a patient’s symptoms, doctors often combine RF testing with a physical exam, imaging tests, and laboratory tests such as CCP antibody testing, antinuclear antibody (ANA) testing, and a synovial fluid analysis.

Limitation

   Diagnosing autoimmune disorders can be complex, so it’s important to work with a doctor when interpreting test results. Patients may also benefit from consulting with a rheumatologist. Rheumatologists are doctors that specialize in diagnosing and treating autoimmune disorders and other conditions of the joints, muscles, and bones. A rheumatologist can help patients understand their test results, as well as answer questions about the process of diagnosing autoimmune disorders.