What is a normal rheumatoid factor?

Results are usually reported in one of two ways:

• Less than 40-60 u/mL
• Less than 1:80 (1 to 80) titer

A low number (normal result) generally means you do not have rheumatoid arthritis or Sjogren syndrome. However, these conditions still can still occur in some people who have have a "normal" or low rheumatoid factor (RF).

Normal value ranges may vary slightly among different laboratories.

Rheumatoid factor (RF) blood tests measures the amount of the RF antibody in the blood.

The results of the rheumatoid factor (RF) test may be reported in titers or units:

A titer is a measure of how much the blood sample can be diluted before RF can no longer be detected. A titer of 1 to 20 (1:20) means that RF can be detected when 1 part of the blood sample is diluted by up to 20 parts of a salt solution (saline). A larger second number means there is more RF in the blood. Therefore, a titer of 1 to 80 shows more RF in the blood than a titer of 1 to 20.

Nephelometry units indicate how much light is blocked by the blood sample in the tube. A high level of RF causes the sample to be cloudy, so less light passes through the tube than when the RF level is low. So an RF level of 100 units is higher than one of 40 units.

Normal

Normal values vary from lab to lab. Results are usually available in a day or two.

Rheumatoid factor (RF) Titers

1:20 to 1:80 Units

14 units/mL to 60 units/mL

Patients should check with their heath profesional to see what the normal range is for the lab that tested your blood.

Rheumatoid factor is an immunoglobulin (antibody) which is able to bind to other antibodies. Rheumatoid factor is usually not found in the general population. it is only found in about 1-2% of healthy people. Rheumatoid factor increases with age and about 20% of people over 65 years old have an elevated rheumatoid factor.

A blood test is done to detect the presence of rheumatoid factor. This is normally ordered to diagnose rheumatoid Arthritis. Rheumatoid factor is present in 80% of adults who have rheumatoid arthritis The incidence of rheumatoid factor increases with duration time: at 3 months the incidence is 33%, at one year it is 75%. Up to 20% of rheumatoid arthritis sufferers remain negative for rheumatoid factor (also known as "seronegative rheumatoid arthritis") throughout their disease.

Results are usually reported in one of two ways:

Normal values are LESS than 60 U/ml.

A low number (normal result) usually means you do not have rheumatoid arthritis or Sjogren syndrome. However, some people who do have these conditions still have a "normal" or low rheumatoid factor (RF).