How do I prepare for a rheumatoid factor blood test?
You don’t need to do anything special to get ready for a rheumatoid factor blood test. You can eat, drink and do all your usual activities.
Your provider may take a sample of your blood during a routine physical exam or if you visit them after noticing new symptoms. They might ask you to visit a phlebotomist (blood draw specialist) at a separate appointment.
What happens during the test?
The RF test is just like any other blood draw you may have had before. Your provider or a phlebotomist will take a sample of your blood from a vein on the inside of your elbow or the back of your hand. Tell your provider if you don’t like needles or feel stressed during blood draws. They’ll help you relax and feel comfortable before and during the test.
Your provider or phlebotomist will:
- Clean the area with an antiseptic wipe.
- Put an elastic band around your upper arm that puts light pressure on it. They may ask you to make a fist or squeeze your hand, too. (Both actions encourage blood to flow to your arm and hand to make it easier to get a sample.)
- Gently insert a needle into your arm or hand. You might feel a sharp pinch. Try to keep your arm relaxed and breathe normally.
- Collect a sample of your blood in a vial.
- Remove the needle and put a bandage over the spot where they inserted it.
It’s less common, but your provider might have you do a rheumatoid factor test at home with a finger prick kit. You’ll poke the tip of your finger yourself with the provided needle (lancing device) and collect the blood on a special strip of paper. Follow all the directions that come with the RF test kit, including how to safely package and ship the sample.
What happens after the test?
After your provider or phlebotomist collects a sample of your blood, that’s it. You don’t need to do anything else. They’ll send the sample to a lab for analysis.
What are the risks of this test? Are there side effects?
There are very few risks to having a rheumatoid factor test.
Some people feel dizzy or lightheaded after a blood draw. You may need to rest a few minutes before standing up or moving. Even if you experience these side effects, they usually only last a few minutes at most.
FAQs
A normal, healthy amount of rheumatoid factor is less than 20 units per milliliter (<20 U/mL). Your provider might also refer to your test as being negative or positive. A negative result means you have a normal amount of RF in your blood. Positive means you have high levels of rheumatoid factor.
What is considered a high rheumatoid factor? ›
A person's risk of developing rheumatoid arthritis typically increases with their RF level. The authors of the 2012 study report that a person with an RF level of 100 U/ml or higher may be up to 26 times more likely to develop rheumatoid arthritis than a person with an RF level under 25 U/ml.
What number is a positive rheumatoid factor? ›
Negative levels do not exclude the disease, and positive levels do not guarantee the diagnosis. The normal range of RF is from 0-20 IU/ml. RF above 20 IU/ml is not considered enough to diagnose RA, as there other reasons the RF level may be elevated.
What is the normal range for RA test? ›
The normal range is the same for both genders, typically less than 14 IU/mL. Values above 14 IU/mL suggest abnormal results, possibly indicating rheumatoid arthritis or inflammatory disorders. Consult a healthcare professional for proper interpretation and evaluation. Can the RA factor change from negative to positive?
What does a rheumatoid factor of 36 mean? ›
Normal Rheumatoid Factor Levels
Always talk with your doctor to learn more about your test results. The normal range of rheumatoid factor levels is usually between < 14 and < 20 IU/mL. A level above these values is considered a positive result and may indicate rheumatoid arthritis or other disorders [9, 10, 11].
What is a safe range for rheumatoid factor? ›
A normal, healthy amount of rheumatoid factor is less than 20 units per milliliter (<20 U/mL). Your provider might also refer to your test as being negative or positive. A negative result means you have a normal amount of RF in your blood.
What autoimmune diseases have a high rheumatoid factor? ›
Patients with rheumatic diseases like Sjogren syndrome, mixed connective tissue diseases, mixed cryoglobulinemia, and systemic lupus erythematosus (SLE) have elevated RFs.
How to read rheumatoid factor results? ›
The normal range of RF is often considered to be 0 to 20 IU/ml (also referred to as RF negative) but sometimes a rheumatoid factor greater than or equal to 15 IU/ml is considered to be elevated, or RF positive. A reading above 20 IU/ml is considered high.
What is a weak positive rheumatoid factor? ›
Some healthy people — usually older people — have positive rheumatoid factor tests, though it's not clear why. And some people who have rheumatoid arthritis will have low levels of rheumatoid factor in their blood. Cigarette smokers also may have positive rheumatoid factors.
Is RA factor 3.5 normal? ›
The "normal" range (or negative test result) for rheumatoid factor is less than 14 IU/ml. Any result with values 14 IU/ml or above is considered abnormally high, elevated, or positive.
The new criteria are as follows: 1) morning stiffness in and around joints lasting at least 1 hour before maximal improvement; 2) soft tissue swelling (arthritis) of 3 or more joint areas observed by a physician; 3) swelling (arthritis) of the proximal interphalangeal, metacarpophalangeal, or wrist joints; 4) symmetric ...
What is stage 3 RA? ›
Stage 3 is when patients begin to experience more severe forms of joint inflammation and pain. Rheumatoid nodules, which are firm lumps under the skin, may also begin to form. As RA progresses, joint damage becomes more pronounced, affecting both form and function.
What is a high number for RA? ›
A rheumatoid factor level over 100 is strongly associated with autoimmune diseases like RA. To compare, typical findings are less than 60 u/ml. In addition to RA, a high rheumatoid factor can also point to cancer, chronic infections, Sjögren's disease, bacterial endocarditis, or other autoimmune disorders.
What is the scale for rheumatoid arthritis? ›
The Rheumatoid Arthritis Severity Scale (RASS) scores disease activity, functional impairment, and physical damage. Doctors rate each category by asking questions and performing examinations. The maximum RASS score is 300. Doctors rarely use the RASS anymore.
What does a rheumatoid factor of 400 mean? ›
High levels (> 400 IU/ml) are most common in Rheumatoid Arthritis and/or Sjögrens syndrome especially associated with vasculitis or cryoglobulinaemia. High levels can also be found in bacterial endocarditis where they fall after effective treatment.
What is the severity scale for rheumatoid arthritis? ›
The Rheumatoid Arthritis Severity Scale (RASS) scores disease activity, functional impairment, and physical damage. Doctors rate each category by asking questions and performing examinations. The maximum RASS score is 300. Doctors rarely use the RASS anymore.
