Rheumatoid arthritis (RA) is a complex autoimmune disorder, and diagnosing it often involves a variety of blood tests. One key test is for rheumatoid factor (RF), a protein produced by the immune system that can attack healthy tissue in the body. Historically, a positive RF test, especially when accompanied by joint inflammation, was strongly indicative of RA. Today, this test is still significant, but other factors are also considered.
A positive rheumatoid factor test indicates a high level of RF in the blood, closely associated with autoimmune diseases, particularly RA. To diagnose seropositive RA, patients must test positive for rheumatoid factor and/or anti-cyclic citrullinated peptide (anti-CCP) antibodies. Anti-CCP testing is a newer, more sensitive method than RF testing. Although about 80% of adult RA patients test positive for RF, it’s important to note that RF can be present in individuals without autoimmune disorders.
The causes of rheumatoid factor development in the blood are not fully understood. However, several blood tests are utilized for diagnosing RA, including:
Erythrocyte sedimentation rate (ESR)
C-reactive protein (CRP)
Full blood count (CBC)
Rheumatoid factor
CCP antibodies
Antinuclear antibodies (ANA)
A positive ANA test indicates the presence of antinuclear antibodies. While a positive ANA test does not conclusively diagnose RA, it may point to an autoimmune condition or an infection causing the positive result.
For more information on RA blood tests and rheumatoid factor, visit RheumatoidArthritis.org, the Mayo Clinic, RheumatoidArthritis.org on Seropositive RA, RheumatoidArthritis.org on Rheumatoid Factor, Healthline, and Verywell Health.
