RF IgM

Understanding the marker

Rheumatoid factor is an antibody measured when assessing some joint symptoms. It can be present with or without rheumatoid arthritis.

Rheumatoid factor supports assessment when rheumatoid arthritis is clinically suspected. It may be positive in other conditions and in people without rheumatoid arthritis. Negative antibodies must not delay referral for persistent synovitis. Results use the performing laboratory assay and reference interval.

What does a positive RF IgM result mean?

A positive result does not identify a cause on its own. Joint symptoms, an examination and other tests, including anti-CCP when relevant, help establish its meaning.

What does a negative RF IgM result mean?

Negative RF makes RA less likely but does not rule out the disease.