To help diagnose the presence of an autoimmune disease such as rheumatoid arthritis (RA)
When you have joint pain and fatigue that your healthcare practitioner suspects may be due to RA
A blood sample drawn from a vein in your arm
Rheumatoid factor (RF) is an autoantibody, an immunoglobulin M (IgM) protein that is produced by the body's immune system. Autoantibodies attack a person's own tissues, mistakenly identifying the tissue as "foreign." While the biologic role of RF is not well understood, its presence is useful as an indicator of inflammatory and autoimmune activity. This test detects and measures RF in the blood and may be used, along with other tests, to help in the diagnose of rheumatoid arthritis (RA).
RA is a chronic, systemic autoimmune disease that causes inflammation, pain, stiffness, and destructive changes in the hands, feet, and other joints throughout the body. Some patients may show signs of fatigue, low-grade fevers, and weight loss.
It can affect anyone at any age but usually develops in the late child-bearing years in women and between the ages of 60 to 80 in men. Over 70% of those affected with RA are women. The course of RA and its prognosis are variable. It may develop and progress slowly or rapidly. It may go into remission in some people and, in a few, it may go away. Left untreated, RA can shorten a person's lifespan and can, within a few years, leave many of those affected too disabled to work.
There are a variety of treatments available to minimize the complications of RA, but they depend on making an accurate diagnosis and on beginning treatment before the development of significant joint damage.
Rheumatoid factor has been used to detect RA. Because the sensitivity and specificity of RF are not ideal, other laboratory tests are often performed in conjunction with RF testing. About 80% of those with RA will have a positive RF test, but it can be negative in people who have clinical signs of RA.
A test for cyclic citrullinated peptide antibodies (CCP) may be done along with an RF test as studies have shown that the CCP antibody test has a sensitivity and specificity that is considered better than RF and is more likely to be positive with early RA. Other tests that may be performed are:
Elevated RF can be found in a small percentage (5-10%) of healthy people. RF may also be elevated in the elderly, though they may not demonstrate clinical signs. In addition, elevated levels of RF may be detected in people who do not have RA (false positive) but may have another disorder:
The rheumatoid factor (RF) test is used in conjunction with other laboratory tests and imaging tests (X-rays, ultrasound, MRI) to diagnose rheumatoid arthritis (RA) and to help distinguish RA from other forms of arthritis or other conditions that cause similar symptoms.
While diagnosis of RA relies heavily on the clinical picture, some of the signs and symptoms may not be present or follow a typical pattern, especially early in the disease. Furthermore, the signs and symptoms may not always be clearly identifiable since people with RA may also have other connective tissue disorders or conditions, such as Raynaud phenomenon, scleroderma, autoimmune thyroid disorders, and systemic lupus erythematosis, and display symptoms of these disorders as well. The RF test is one tool among others that can be used to help make a diagnosis when RA is suspected.
The test for RF may be ordered when a person has signs and symptoms of RA. Symptoms may include:
An RF test may be repeated when the first test is negative and symptoms persist.
The RF test must be interpreted in conjunction with other laboratory tests and a person's signs, symptoms, and clinical history. RF is present in 70%-90% of patients with RA, though is not diagnostic of RA.
In those with symptoms and clinical signs of rheumatoid arthritis, the presence of significant concentrations of RF indicates that it is likely that they have RA. Higher levels of RF generally correlate with more severe disease and a poorer prognosis.
A negative RF test does not rule out RA. About 20% of people with RA will have very low levels of or no detectable RF. In these cases, a CCP antibody test may be positive and used to confirm RA.
The 2010 Rheumatoid Arthritis Classification Criteria from the American College of Rheumatology (ACR) includes cyclic citrullinated peptide (CCP) antibody testing, along with RF, as part of its criteria for diagnosing rheumatoid arthritis. According to the ACR, CCP antibodies may be detected in about 50-60% of people with early RA, as early as 3-6 months after the beginning of symptoms. Early detection and diagnosis of RA allows healthcare practitioners to begin aggressive treatment of the condition, minimizing the associated complications and tissue damage.
That depends on the laboratory performing the test. Not every lab performs this test and your sample may be sent to a reference laboratory for testing. It may take 2 to 3 days for results to be available.
Sources Used in Current Review
Smith, H. and Brown, A. (2018 January 29, Updated). Rheumatoid Arthritis. Medscape Rheumatology. Available online at https://emedicine.medscape.com/article/331715-overview. Accessed on 3/18/18.
(© 1995–2018). Rheumatoid Factor, Serum. Mayo Clinic Mayo Medical Laboratories. Available online at https://www.mayomedicallaboratories.com/test-catalog/Overview/9060. Accessed on 3/18/18.
Starkebaum, G. et. al. (2017 April 24, Updated). Rheumatoid factor (RF). MedlinePlus Medical Encyclopedia. Available online at https://medlineplus.gov/ency/article/003548.htm. Accessed on 3/18/18.
(2017 April 30, Reviewed). Rheumatoid Arthritis. National Institute of Arthritis and Musculoskeletal and Skin Diseases. Available online at https://www.niams.nih.gov/health-topics/rheumatoid-arthritis/advanced#tab-overview. Accessed on 3/18/18.
Delgado, J. et. al. (2018 March, Updated). Rheumatoid Arthritis – RA. ARUP Consult. Available online at https://arupconsult.com/content/rheumatoid-arthritis. Accessed on 3/18/18.
Street, T. and Schmidt, S. (2014 March 16, Updated). Rheumatoid Factor. Medscape Laboratory Medicine. Available online at https://emedicine.medscape.com/article/2087091-overview#showall. Accessed on 3/18/18.
Ingegnoli, F. et al. (2013 November 13). Rheumatoid Factors: Clinical Applications. Dis Markers. 2013; 35(6): 727–734. Available online at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3845430/. Accessed on 3/18/18.
© 2018 American College of Rheumatology. ACR-endorsed Criteria for Rheumatic Diseases. Available online at https://www.rheumatology.org/Practice-Quality/Clinical-Support/Criteria/ACR-Endorsed-Criteria. Accessed May 2018.
Sources Used in Previous Reviews
Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition]. Pp 1681.
Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO. Pp 749-750.
Peng, S. (2005 April 20). Rheumatoid Factor. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003548.htm.
Rindfleisch, J. A. and Muller, D. (2005 September 15). Diagnosis and Management of Rheumatoid Arthritis. American Family Physician [On-line journal]. Available online at http://www.aafp.org/afp/20050915/1037.html.
(© 2006). Rheumatoid Factor. ARUP's Guide to Clinical Laboratory Testing [On-line information]. Available online at http://www.aruplab.com/guides/clt/tests/clt_196b.jsp#1147119.
Borigini, M.J. (Updated 2009 May 31). Rheumatoid factor (RF). MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003548.htm. Accessed March 2009.
(Revised 2009 April). Handout on Health: Rheumatoid Arthritis, National Institute of Arthritis and Musculoskeletal and Skin Diseases [On-line information]. Available online at http://www.niams.nih.gov/Health_Info/Rheumatic_Disease/default.asp. Accessed March 2009.
Borigini, M.J. (Updated 2010 February 7). Rheumatoid Arthritis. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000431.htm. Accessed March 2009.
Smith, H. (Updated February 22). Rheumatoid Arthritis. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/331715-overview. Accessed March 2009.
King, R. and Worthington, R. (Updated 2010 January 12). Arthritis, Rheumatoid. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/808419-overview. Accessed March 2009.
Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 825-826.
Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 958-961.
Sjogrens Syndrome Foundation. About Sjogrens syndrome: Diagnosis. Available online at http://www.sjogrens.org/home/about-sjogrens-syndrome/diagnosis. Accessed May 2010.
MedlinePlus Medical Encyclopedia. Rheumatoid factor (RF). Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003548.htm. Accessed March 2014.
Mayo Clinic. Rheumatoid factor. Available online at http://www.mayoclinic.com/health/rheumatoid-factor/MY00241. Accessed March 2014.
MedicineNet.com. Rheumatoid Factor (RF) Blood Test Results and Significance. Available online at http://www.medicinenet.com/rheumatoid_factor/article.htm. Accessed March 2014.
Quest Diagnostics. Rheumatoid Arthritis Laboratory Markers for Diagnosis and Prognosis. Available online at http://www.questdiagnostics.com/testcenter/testguide.action?dc=CF_RheumatoidArthritis#Test%20Selection. Accessed March 2014.
Street T et al. Rheumatoid Factor. Medscape. Available online at http://emedicine.medscape.com/article/2087091-overview#a30. Accessed March 2014.
About.com. What Is Rheumatoid Factor? Available online at http://arthritis.about.com/od/radiagnosis/a/rheumfactor.htm. Accessed March 2014.