What is the Normal Range for a Rheumatoid Factor Test?

Rheumatoid Factor (RF) is a key indicator in diagnosing rheumatoid arthritis, and understanding its normal range is crucial. The normal range for a Rheumatoid Factor test, which measures the level of RF in the blood, is generally considered to be less than 14 IU/ml. Values at or above 14 IU/ml are typically considered elevated and may indicate an autoimmune disorder.

Rheumatoid factor is an autoantibody formed in the immune system, sometimes mistakenly attacking healthy cells and tissues. This is characteristic of autoimmune disorders such as rheumatoid arthritis. It’s important to note that a positive rheumatoid factor is not exclusively specific for rheumatoid arthritis.

Each laboratory may have its own range for what constitutes a normal Rheumatoid Factor level, often depending on the assay used. Most laboratories set their normal range from 0.0 to 14.0 IU/ml. Any level higher than the laboratory’s normal range is deemed abnormal.

Alongside the RF test, other blood tests are frequently used to assist in diagnosing rheumatoid arthritis, including Anti-nuclear antibody (ANA), Anti-cyclic citrullinated peptide (anti-CCP) antibodies, C-reactive protein (CRP), and Erythrocyte sedimentation rate (ESR or sed rate).

It’s also important to differentiate the Rheumatoid Factor test from the Rh factor blood test, which pertains to the presence of a specific protein on red blood cells, influencing blood type.

For more detailed information, visit the following sources:

RheumatoidArthritis.org
MedicineNet
Mayo Clinic – Rh Factor Blood Test
Mayo Clinic – Rheumatoid Factor Test
Johns Hopkins Arthritis Center
Johns Hopkins Arthritis Center – Normal Rheumatoid Factor Levels
MedlinePlus
Verywell Health