A rheumatoid factor (RF) test is an antibody present in the blood. The test checks for the presence of these antibodies. The test is carried out using a set of reagents. A blood sample is taken from a patient.
Rheumatoid factor test
When is the test done?
RF – test indicates in patients suspected of rheumatoid arthritis or Sjogren’s syndrome. This test helps distinguish rheumatoid and inflammatory arthritis from other forms of arthritis. This test can be recommended in other forms of inflammatory conditions.
RF is an anti – antibody. This can be detected in the laboratory due to its ability to bind and form lumps with latex particles or red blood cells that contain human immunoglobulin G (IgG).
If RF is present in the patient’s blood, then it attaches to IgG, covering latex particles, causing lumps. This is called agglutination. Agglutination is considered a positive reaction, which indicates the presence of rheumatoid factor at a detectable level.
RF results can be presented in two ways: less than 40-60 units per milliliter or less than 1:80 titers or from 1 to 80 titers. Values may vary depending on the laboratory and the kit used to verify the factor.
Lower rates indicate the absence of conditions such as RA or Sjogren’s syndrome, but there are several normal healthy people who have a positive rheumatoid factor rating. This makes RF tests an unreliable test, especially in the absence of symptoms.
The significance of abnormal results.
Those with a positive RF have a high level of antibody titers in the blood. Most patients with rheumatoid arthritis and almost all patients with Sjogren’s syndrome have positive test results. If levels are higher, the disease can be more accurately confirmed.
There are several more conditions that show high levels and titers of rheumatoid factor. These include systemic lupus erythematosus or SLE, scleroderma, sarcoidosis, dermatomyositis, etc. Those with viral infections, such as hepatitis, AIDS, flu, infectious mononucleosis, etc., can also be positive for rheumatoid factor. Other infections, such as parasitic infections, bacterial infections, tuberculosis, can also be positive results. Kidney disorders, endocarditis, blood cancer such as leukemia and multiple myelomas, lung and liver diseases also cause an increase in the level of rheumatoid factor.
Risks associated with the testing.
There is a small risk of bleeding, infection, and pain at the place where the blood sample is taken from. Usually, this is a minor risk if a person does not have bleeding and bleeding disorders.
Limitations of the test.
This is not a confirmatory test, as many normal healthy people may experience positive results. In addition, several conditions may show positive titers for this test. The procedure must be followed in detail. Reading agglutination after a set time may lead to false readings. Contamination of agents, samples or material handling equipment leads to erroneous results.
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