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Rheumatoid Factor Blood Test

Last updated April 27, 2018

Approved by: Maulik P. Purohit MD, MPH

The Rheumatoid Factor Blood Test is a test to assess the presence and levels of RF in circulation.

What are the other Names for this Test? (Equivalent Terms)

  • RF Blood Test
  • RF Latex Blood Test

What is Rheumatoid Factor Blood Test? (Background Information)

  • A rheumatoid factor (RF) is a type of immunoglobulin associated with rheumatoid arthritis
  • Immunoglobulins (Igs) are a category of proteins produced by immune cells that aid in bodily defense against outside invaders. They recognize characteristic surface markings (antigens) on a foreign object and bind them away, before any damage is done to the body
  • There are 5 five main types of immunoglobulins; each type, differing in its function and distribution throughout the body. The 5 types are:
    • IgA
    • IgG
    • IgE
    • IgD
    • IgM
  • Immunoglobulins can reside either on the outside of cells, or freely circulate in blood. When circulating, they are also called antibodies (Abs)
  • Problematic antibodies that target the body’s own tissues are called autoantibodies. These autoantibodies are responsible for autoimmune disorders
  • Rheumatoid factor is an IgM, directed against IgG. Thus, RF is an autoantibody and its presence may indicate an autoimmune disorder, most notably rheumatoid arthritis
  • The Rheumatoid Factor Blood Test is a test to assess the presence and levels of RF in circulation

What are the Clinical Indications for performing the Rheumatoid Factor Blood Test?

Following are the clinical indications for performing a Rheumatoid Factor Blood Test:

  • Signs and symptoms that affect the joints, which include:
    • Stiffness
    • Pain
    • Inflammation

How is the Specimen Collected for Rheumatoid Factor Blood Test?

Following is the specimen collection process for Rheumatoid Factor Blood Test:

Sample required: Blood

Process: Insertion of a needle into an arm vein.

Preparation required: No special preparation is needed prior to the test.

What is the Significance of the Rheumatoid Factor Blood Test Result?

A positive Rheumatoid Factor Test may indicate rheumatoid arthritis, in 75% of the cases. Additionally, the following conditions and infections are associated with rheumatoid factor:

  • Syphilis
  • Sjögren syndrome
  • Essential mixed cryoglobulinemia
  • Infective endocarditis
  • Tuberculosis
  • Cirrhosis
  • Systemic lupus erythematosus
  • Sarcoidosis
  • Primary pulmonary fibrosis
  • Old age

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • Rheumatoid factor is not specific to rheumatoid arthritis. Thus, having a positive RF does not necessarily indicate rheumatoid arthritis
  • This test may be performed alongside imaging tests, such as an X-ray, to gain a better understanding of the clinical scenario

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

References and Information Sources used for the Article:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: June 13, 2014
Last updated: April 27, 2018