Introduction
Rheumatoid factor is an immunoglobulin (Ig) discovered about 70 years ago. Rose first identified specific antibodies among rheumatoid arthritis (RA) patients in 1948, and they were termed rheumatoid factors in 1952 because of their relationship to the disease. Although they were first discovered in RA patients, RFs can also be detected in patients with various autoimmune and non-autoimmune disorders and in healthy people. Antibodies targeting the Fc region of immunoglobulin G, known as rheumatoid factors, come in various isotypes and affinities. Other immunoglobulin types, such as IgG and IgA, were hardly seen. The most prevalent RF is IgM.
What Are the Functions of Rheumatoid Factor?
Without immunogenic stimulation, rheumatoid factors are not detectable in circulation. They are thought to be a natural reaction to various antigenic stimuli, such as toxic compounds like lipopolysaccharides or pathogens like the Epstein-Barr virus (EBV). They produce immunological complexes, which are then phagocytosed by inflammatory cells. These RFs are transitory, low-affinity polyclonal antibodies produced by the germ cells. In this situation, their position could be termed protective.
A complicated interaction between B-lymphocytes, T-lymphocytes, and dendritic cells is involved in the pathophysiology of RA. Loss of tolerance to citrulline-containing proteins is caused by various environmental and genetic causes, resulting in autoantibodies such as anti-cyclic citrullinated protein antibodies (ACPA) and RF.
It is probable that this antigenic input also triggers the synthesis of RF that produces B cells, which perform isotype switching and keep the inflammatory reaction continuing. Additional activation and adhesion of inflammatory cells such as macrophages, neutrophils, and lymphocytes may result from the involvement of RF in complex immune development. This causes tissue damage and creates a positive feedback loop in which more autoantibodies are produced. Such a mechanism could explain an autoimmune and self-sustaining inflammatory response that eventually leads to arthritis.
What Disorders Are Associated With High Rheumatoid Factor Levels?
Disorders associated with high Rheumatoid Factor levels:
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Systemic Lupus Erythematosus (SLE).
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Mixed Connective Tissue Disease (MCTD).
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Scleroderma.
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Hepatitis B.
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Hepatitis C.
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Tuberculosis.
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Endocarditis.
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Sarcoidosis.
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Interstitial Lung Disease (ILD).
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Inflammatory Bowel Disease (IBD).
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Lymphoma.
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Multiple Myeloma.
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Chronic Liver Disease.
What Is the Test for Rheumatoid Factor?
The rheumatoid factor (RF) concentration in the blood is measured by the rheumatoid factor (RF) test. The rheumatoid factor blood test is the most commonly used test to diagnose rheumatoid arthritis. Rheumatoid factors can also indicate the presence of other autoimmune diseases, such as juvenile arthritis, infections, and cancer. This test is done by collecting a little blood sample from a vein in your arm during a rheumatoid factor test. This usually only takes a few minutes. A sample of blood is submitted to a laboratory for testing.
When to Do the Rheumatoid Factor Test?
A blood test for rheumatoid arthritis can be done when the patient has symptoms like joint pain, early morning stiffness, swelling, generalized weakness, and a mild increase in temperature.
What Is the Clinical Significance of Rheumatoid Factor?
The presence or absence of rheumatoid factors and their titers and isotypes have outstanding value for the diagnosis and prognosis of rheumatoid arthritis. Seropositive RA patients may have severe and erosive joint disease and extra-articular symptoms like rheumatoid nodules and vasculitis, whereas seronegative patients may not. Similarly, high RF titers increase the chances of a patient developing RA and, consequently, a worse prognosis. Furthermore, RF appears at different times in RA patients. Some people get RF before they develop clinical illness.
The early emergence of RF in these patients has been related to a more severe illness. Most asymptomatic people with a positive RF, on the other hand, do not develop RA. However, a group of patients develops RF after experiencing symptoms. The mechanism that causes this variation is unknown.
The sensitivity and specificity of RF testing in RA patients are 60 to 90 percent and 85 percent, respectively. The normal range of rheumatoid factors can vary, and sensitivity can range from 26 percent to 90 percent, depending on the subject and control group used. Testing for rheumatoid arthritis, such as with the rheumatoid arthritis blood test results, can be used alongside clinical manifestations and ACPA testing to enhance diagnosis. ACPA testing offers higher specificity than RF, especially for early rheumatoid arthritis, and helps improve the accuracy of diagnosing the disease.
RFs have limited clinical usefulness in predicting RA prognosis and therapy response. It is not suggested that RF monitoring be used just to track RA disease activity. However, it may have a role in predicting the therapeutic efficacy of some therapeutic drugs. Increased pretreatment levels of RF, for example, have been linked to a poor therapeutic outcome of TNF-alpha medications, and seropositive RA patients have a stronger response to Rituximab than seronegative RA patients.
Conclusion
Patients with arthritis/arthralgia should not be tested for RFs unless there is a high clinical suspicion of RA. However, if the individual has already been confirmed with RA, consultation with a rheumatologist is recommended. Rheumatologists who are involved early in the management of RA patients had better outcomes of normal function and disability of the joint. The general practitioner and the rheumatologist must work together to achieve a positive illness outcome.
