Posted by 
Rheumatoid factor is an immune system protein. Doctors can measure its levels using a blood test to help diagnose autoimmune conditions, including rheumatoid arthritis. A rheumatoid factor (RF) test is a blood test that can help diagnose rheumatoid arthritis (RA).
High RF levels can indicate RA, but it is only one aspect of a full diagnosis. High RF can also occur in people with other conditions or those with no health issues. In some cases, people with an autoimmune condition have normal RF levels.
Blood draw being taken for sample and test. A doctor may recommend a blood test to measure RF levels. RF is a type of protein called an autoantibody. The immune system makes RF. Doctors do not yet fully understand the role RF plays in the body.
In people with an autoimmune condition, RF can attack healthy cells. The immune system mistakes healthy cells for foreign bodies and typically creates higher levels of RF to attack these cells. An RF test is one test doctors use to help diagnose autoimmune conditions.
Higher levels of RF in the body can be an indication that there is some level of autoimmune activity happening, which can mean the presence of an underlying condition.According to the Hospital for Special Surgery, the normal RF range is between 0–20 units per milliliter of blood (u/ml).
Having RF levels above this range is not enough to diagnose RA.High RF levels, or positive results, indicates that there is a lot of RF in the blood. A concentration of RF can be a sign of inflammation and autoimmune disruption.
Around 80% of people with RA have significant concentrations of RF in their blood. In the early stages of arthritis, some 30% of people may have raised levels of RF.
However, higher levels of RF can also occur in other conditions, and a small percentage of people without a medical condition, though the exact reason for this is uncertain.
Autoantibodies can also occur as part of the natural aging process. According to one study, 5% of healthy 50-year-olds may have high RF, and 10–25% of people aged 70 years.
If a person has abnormally high RF levels and also experiences symptoms of RA, it is likely they have RA.
Signs of RA can include:
pain and stiffness in the joints
swelling and inflammation in the joints
loss of range of motion
nodules under the skin
general fatigue
How high the RF results are may play into a doctor’s diagnosis. Very high levels can be more indicative of RA than lower levels, as this indicates more activity in the immune system.Treatment for high RF depends on treating the underlying cause.
In people with RA, the goal of treatment is to slow the progression of the disorder and help prevent or reduce symptoms. There is no outright cure for RA. However, effective, early treatment will stop or slow down disease progression and prevent permanent joint damage.