Rheumatoid Factor Test

The rheumatoid factor is an antibody present in the blood of many patients with rheumatoid arthritis. Doctors measure the level of rheumatoid factor by performing a blood test. A positive rheumatoid factor test means that the patient’s level of rheumatoid factor in their blood  is considered high.

Rheumatoid factor was first described in connection to rheumatoid arthritis in 1940. For decades, a positive rheumatoid arthritis test was used to diagnose those with symptoms of rheumatoid arthritis.

Today, a positive rheumatoid factor test is mostly used as a supportive tool in helping doctors reach a diagnosis. Yet, it must be combined with other tools and criteria. A positive rheumatoid factor test is also used to determine a general prognosis for rheumatoid arthritis in adults and children.

What is Rheumatoid Factor?

All immune systems contain healthy antibodies that fight off infections caused by bacteria and viruses. Sometimes, however, bad antibodies are produced by the immune system which can attack healthy antibodies. In other words, the antibodies turn against the person’s system damaging their health.

When antibodies begin to attack the person, it can result in triggering an immune response. This immune response can turn into an autoimmune disorder which in turn can produce a variety of different symptoms, ultimately damaging that person’s health.

Rheumatoid factor is a bad protein antibody produced by a person’s immune system. If triggered, rheumatoid factor antibodies attack the healthy tissue in the patient’s body. Rheumatoid factor attacks result in a variety of inflammatory symptoms.

Typically, these symptoms cause inflammation in the synovium of the patient’s joints, which leads to rheumatoid arthritis. Rheumatoid factor can also cause other symptoms seen in autoimmune disorders like Sjogren’s Syndrome or Hepatitis C.

The reason rheumatoid factor is commonly associated with rheumatoid arthritis specifically is because when the antibody was discovered it was used to diagnose rheumatoid arthritis. Approximately 80% of adult rheumatoid arthritis patients test positive for rheumatoid factor. However, people without any autoimmune disorders can also test positive for rheumatoid factor.

What Causes Rheumatoid Factor?

It is unknown what causes rheumatoid factor to develop in someone’s blood. It is thought to be however a combination of genetics and other external risk factors. Certain people have low levels of rheumatoid factor, which may not ever be enough to trigger an autoimmune response.

On the other hand, some people have high levels of rheumatoid factor and go on to develop autoimmune disorders like rheumatoid arthritis. It isn’t known what triggers the autoimmune response that causes rheumatoid arthritis.

How to Test for Rheumatoid Factor

Testing for rheumatoid factor is like any other blood test. The rheumatoid factor test is done by drawing blood and analyzing it for the presence of this particular protein antibody. If the results show a certain level of rheumatoid factor, then the test reads positive for rheumatoid factor. Rheumatoid factor tests can also detect lower levels of rheumatoid factor that don’t result in it being declared a positive reading.

What Do Rheumatoid Factor Test Results Mean?

Testing positive for rheumatoid does not necessarily mean the patient has rheumatoid arthritis. A positive for rheumatoid factor test results means that it can lead to or is the cause of inflammatory symptoms from an autoimmune disorder.

In certain cases, however, patients may test positive for rheumatoid factor and remain healthy never to experience symptoms.

Rheumatoid factor can be present in patients several months or even years before clinical rheumatoid arthritis symptoms develop. Depending on the level of symptoms a patient exhibits, the rheumatoid factor test results can assist doctors in reaching a rheumatoid arthritis diagnosis.

Positive rheumatoid factor results in someone who has been clinically diagnosed with rheumatoid arthritis may also indicate the potential for a more aggressive disease course. This is possible in both children and adult patients.

Patients who test negative for rheumatoid factor but still exhibit symptoms and meet other diagnostic criteria may still be diagnosed with rheumatoid arthritis.

Diagnosing Rheumatoid Arthritis with Rheumatoid Factor Test

Patients who test positive for rheumatoid factor aren’t necessarily diagnosed with rheumatoid arthritis right away. There must also be a clear history of consistent rheumatoid arthritis symptoms.

If your doctor suspects symptoms of rheumatoid arthritis, other criteria must first be taken into consideration before reaching a diagnosis. The presence of rheumatoid factor alone does not typically lead to an immediate rheumatoid arthritis diagnosis. Doctors look at physical symptoms, medical history and may conduct other blood tests, like anti-CCP, and imaging scans to help identify the condition.

Depending on the final diagnosis, the presence of rheumatoid factor in a patient’s blood may help determine the type of treatment that will be provided to that patient, such as disease-modifying antirheumatic drugs (DMARDs).

A positive rheumatoid factor test along with a rheumatoid arthritis diagnosis can potentially help the doctor determine a prognosis, although this depends on a variety of factors.

How Rheumatoid Factor Affects Prognosis

Determining a prognosis for rheumatoid arthritis patients is difficult. The disease affects different people in different ways. A prognosis can depend largely on the types of symptoms the patient displays as well as their medical history.

Many doctors and researchers feel that a positive rheumatoid factor test result may predict a more severe pattern of symptoms and overall disease course. Extra-articular symptoms like rheumatoid nodules may be more likely to form in patients who have positive rheumatoid factor blood test results. Other aggressive symptoms, though rare, could be more likely to occur in rheumatoid factor positive patients. These may include lung and heart conditions.

Rheumatoid factor positive patients may also have a higher disease activity score, meaning frequent flare-ups and fewer remission periods.

Keep in mind this isn’t always the case. If rheumatoid factor is tested and symptoms are detected early, a diagnosis can be quickly reached. Treatment can begin as soon as possible to prevent further progression of joint damage, swelling and pain.