Also Known As
RF
This article was last reviewed on
This article waslast modified on September 10, 2018.
At a Glance
Why Get Tested?

To help diagnose the presence of an autoimmune disease such as rheumatoid arthritis (RA)

When To Get Tested?

When you have joint pain and fatigue that your healthcare practitioner suspects may be due to RA

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

None

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

What is being tested?

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 chronicsystemic 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:

Accordion Title
Common Questions
  • How is it used?

    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.

  • When is it ordered?

    The test for RF may be ordered when a person has signs and symptoms of RA. Symptoms may include:

    • Pain, warmth, swelling, and morning stiffness in the joints 
    • Nodules under the skin 
    • If the disease has progressed, evidence on X-rays of swollen joint capsules and loss of cartilage and bone 

     

    An RF test may be repeated when the first test is negative and symptoms persist.

  • What does the test result mean?

    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.

  • Is there anything else I should know?

    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.

  • How long will it take for my results to be available?

    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.

View Sources

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.

Ask a Laboratory Scientist

This form enables you to ask specific questions about lab tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science.

Disclaimer
Thank you for using the Consumer Information Response Service ("the Service") to inquire about the meaning of your lab test results.  The Service is provided free of charge by the American Society for Clinical Laboratory Science, which is one of many laboratory organizations that supports Lab Tests Online.
Please note that information provided through this free Service is not intended to be medical advice and should not be relied on as such. Although the laboratory provides the largest single source of objective, scientific data on patient status, it is only one part of a complex biological picture of health or disease. As professional clinical laboratory scientists, our goal is to assist you in understanding the purpose of laboratory tests and the general meaning of your laboratory results. It is important that you communicate with your physician so that together you can integrate the pertinent information, such as age, ethnicity, health history, signs and symptoms, laboratory and other procedures (radiology, endoscopy, etc.), to determine your health status. The information provided through this Service is not intended to substitute for such consultations with your physician nor specific medical advice to your health condition.
By submitting your question to this Service, you agree to waive, release, and hold harmless the American Society for Clinical Laboratory Science and its affiliates or their past or present officers, directors, employees, agents, and Service volunteers (collectively referred to as "ASCLS") and the American Association  for Clinical Chemistry and its affiliates or their past or present officers, directors, employees, agents, and Service volunteers (collectively referred to as "AACC") from any legal claims, rights, or causes of action you may have in connection with the responses provided to the questions that you submit to the Service.
AACC, ASCLS and its Service volunteers disclaim any liability arising out of your use of this Service or for any adverse outcome from your use of the information provided by this Service for any reason, including but not limited to any misunderstanding or misinterpretation of the information provided through this Service.