Rheumatoid factor is an autoantibody

Autoantibody

An autoantibody is an antibody manufactured by the immune system that is directed against one or more of the individual's own proteins. It is derived from the Greek "auto" which means "self", "anti" which means "against" and "body"...

 (antibody

Antibody

An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...

 directed against an organism's own tissues) most relevant in rheumatoid arthritis

Rheumatoid arthritis

Rheumatoid arthritis is a chronic, systemic inflammatory disorder that may affect many tissues and organs, but principally attacks synovial joints. The process produces an inflammatory response of the synovium secondary to hyperplasia of synovial cells, excess synovial fluid, and the development...

. It is defined as an antibody

Antibody

An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...

 against the Fc portion of IgG. RF and IgG join to form immune complex

Immune complex

An immune complex is formed from the integral binding of an antibody to a soluble antigen. The bound antigen acting as a specific epitope, bound to an antibody is referred to as a singular immune complex....

es that contribute to the disease

Disease

A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

 process. RF is part of the latest classification criteria of Rheumatoid Arthritis but has got company of the biomarker ACPA (Anti Citrullinated Peptide Antibody).

Rheumatoid factor can also be a cryoglobulin (antibody that precipitates on cooling of a blood sample); it can be either type 2 (monoclonal IgM

IGM

IGM as an acronym or abbreviation can refer to:* Immunoglobulin M , the primary antibody against A and B antigens on red blood cells* International Grandmaster, a chess ranking* intergalactic medium* Intragroup medium - see: Intracluster medium...

 to polyclonal IgG) or type 3 (polyclonal IgM to polyclonal IgG) cryoglobulin.

Testing

RF is often evaluated in patients suspected of having any form of arthritis

Arthritis

Arthritis is a form of joint disorder that involves inflammation of one or more joints....

 even though positive results can be due to other causes, and negative results do not rule out disease. But, in combination with signs and symptom

Symptom

A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...

s, it can play a role in both diagnosis and disease prognosis

Prognosis

Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...

. It is part of the usual disease criteria of rheumatoid arthritis.

The presence of rheumatoid factor in serum can also indicate the occurrence of suspected autoimmune activity unrelated to rheumatoid arthritis, such as that associated with tissue or organ rejection. In such instances, RF may serve as one of several serological

Serology

Serology is the scientific study of blood serum and other bodily fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum...

 markers for autoimmunity.

Interpretation

High levels of rheumatoid factor (in general, above 20 IU/mL, 1:40, or over the 95th percentile

Percentile

In statistics, a percentile is the value of a variable below which a certain percent of observations fall. For example, the 20th percentile is the value below which 20 percent of the observations may be found...

; there is some variation among labs) occur in rheumatoid arthritis (present in 80%) and Sjögren's syndrome

Sjögren's syndrome

Sjögren's syndrome , also known as "Mikulicz disease" and "Sicca syndrome", is a systemic autoimmune disease in which immune cells attack and destroy the exocrine glands that produce tears and saliva....

 (present in 70%). The higher the level of RF the greater the probability of destructive articular disease. It is also found in Epstein-Barr virus

Epstein-Barr virus

The Epstein–Barr virus , also called human herpesvirus 4 , is a virus of the herpes family and is one of the most common viruses in humans. It is best known as the cause of infectious mononucleosis...

 or Parvovirus

Parvovirus

Parvovirus, often truncated to "parvo", is both the common name in English casually applied to all the viruses in the Parvoviridae taxonomic family, and also the taxonomic name of the Parvovirus genus within the Parvoviridae family...

 infection and in 5-10% of healthy persons, especially the elderly.

There is no association of rheumatoid factor with the level of disease activity.

Rheumatoid factor may also be elevated in: chronic hepatitis

Hepatitis

Hepatitis is a medical condition defined by the inflammation of the liver and characterized by the presence of inflammatory cells in the tissue of the organ. The name is from the Greek hepar , the root being hepat- , meaning liver, and suffix -itis, meaning "inflammation"...

, primary biliary cirrhosis

Primary biliary cirrhosis

Primary biliary cirrhosis, often abbreviated PBC, is an autoimmune disease of the liver marked by the slow progressive destruction of the small bile ducts within the liver. When these ducts are damaged, bile builds up in the liver and over time damages the tissue. This can lead to scarring,...

, any chronic viral infection, bacterial endocarditis, leukemia

Leukemia

Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...

, dermatomyositis

Dermatomyositis

Dermatomyositis is a connective-tissue disease related to polymyositis and Bramaticosis that is characterized by inflammation of the muscles and the skin.- Causes :...

, infectious mononucleosis

Infectious mononucleosis

Infectious mononucleosis is an infectious, widespread viral...

, systemic sclerosis, and systemic lupus erythematosus

Systemic lupus erythematosus

Systemic lupus erythematosus , often abbreviated to SLE or lupus, is a systemic autoimmune disease that can affect any part of the body. As occurs in other autoimmune diseases, the immune system attacks the body's cells and tissue, resulting in inflammation and tissue damage...

(SLE).

History

The test was first described by norwegian Dr Erik Waaler in 1940 and redescribed by Dr H.M. Rose and colleagues in 1948. Redescription is said to be due to the uncertainties due to World War 2. It is still referred to as the Waaler-Rose test.

External links

• MedlinePlus on RF
• Labtestsonline page on RF