Rheumatoid Factor – Introduction, What is It, Tests and Its Significance.

An Introduction To Rheumatoid Factor

Often doctors have to depend on lab tests to help them make an informed diagnosis on a specific condition. In that respect, conditions like rheumatoid arthritis and Sjögren syndrome can be identified by looking for specific markers like Rheumatoid factor (RF).
 
Understanding Rheumatoid Factor

When the immune system mobilizes against a foreign element trying to invade and infect a part of the body, it rushes white blood cells to the site to identify the threat and neutralize it. White blood cells in turn rely on a special protein called antibody that they secrete for performing the infection fighting job. In that respect, an autoantibody is a protein that directs its fighting abilities towards tissues in the body itself.


Rheumatoid factor (RF) is one such autoantibody found in the blood. Given its nature, RF is rarely found in general population, appearing in just 1-2% of healthy population. However, as a person ages, the incidence of the autoantibody i.e. Rheumatoid factor also increases, and that is why its occurrence increases by 20% when one considers people who are 65 years or above.      

Significance Of Rheumatoid Factor

When researchers first studied the relationship of RF with respect to rheumatoid arthritis, they found the protein (RF) to be present in high amounts in roughly 80% of the adult patients suffering from the inflammatory disease.

As such, elevated levels of rheumatoid factor in a person point to a greater chance of him/her having rheumatoid arthritis, rheumatoid modules as well as other autoimmune manifestations that affect organs like the eyes, lungs etc.   

Rheumatoid Factor Tests – What Are They And What Do The Values Mean?

These are blood tests that mainly help in diagnosing autoimmune conditions like rheumatoid arthritis (RA) and Sjögren syndrome. In case of RA, these tests prove essential in differentiating the disease from other forms of arthritis. However, they do not prove to be a definitive option for diagnosing RA given that roughly 30-35% of RA patients can show negative RF results.

Furthermore, rheumatoid factor is much less prevalent in juvenile rheumatoid arthritis (RA found in children 16 years or younger), thus making these tests quite inconclusive when dealing with RA in children.

RF values can be mentioned in terms of percentile, IU/mL, or titer (a type of ratio). Typically, readings of 1:40, above 20 IU/mL or a 95th percentile and upwards will point to good chance of the person suffering from RA or Sjögren syndrome. However, negative values do not mean that the RA is regressing. Instead, it is just the positive RF result that rheumatologists are concerned with.

RF Tests can be categorized into two parts – agglutination tests and nephlometry tests. With agglutination tests, a titer of 1:20 is considered normal. Similarly, 23 units or less of rheumatoid factor measured in nephlometry tests is taken to be normal value.
     
Other Conditions That Exhibit Elevated Rheumatoid Factor

It is possible for a healthy person to exhibit RF, in which case the RF reading is labeled as a ‘false positive’. Furthermore, there can be other autoimmune disorders that may show up a positive rheumatoid factor. This includes the already discussed Sjögren syndrome along with diseases like scheroderma (abnormal growth in connective tissues), polymitosis (a connective tissue disorder that causes degeneration of muscles) and systemic lupus erythematosus. 

Yet, other microbial infections such as tuberculosis, hepatitis, syphilis, osteomyelitis and many others can also exhibit elevated rheumatoid factor. 

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2 Comments

  1. Christy Parenting with Chronic Pain April 2, 2014 1:30 am Reply

    Thank you for taking the time to explain this because my dr ran a panel of tests to check for autoimmune diseases that could be triggering my all over body aches and pain. The good news was my blood work came back within the normal ranges; however, the pain is still there. It is looking like I have fibromyalgia along with my chronic back pain. Talk about a major pain.

  2. Jessy April 3, 2014 1:43 pm Reply

    Hi Christy,

    thank you for commenting on this topic. I'm really glad the post is helpful for you. There will be more posts on such issues published soon, as I write often about medical conditions like that.
    I hope that your next tests results will be much better and you will have your normal, pain free health back again. Just keep living healthy and I am sure the positive results and change will come.

    I wish you all the best.

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