Rheumatoid Arthritis Blood Tests—Decoded
Certain blood tests can help your healthcare provider confirm your RA diagnosis. Learn what they are and how they work.
In addition to a physical exam and X-rays, your doctor may use the following blood tests to confirm a diagnosis of rheumatoid arthritis (RA), check the progression of the disease or gauge how well your current medication is working. Here’s a rundown of the tests and what the results could mean.
Rheumatoid factor (RF): This antibody is found in the blood of about 80% of people with RA. A high level of RF in the blood signals that your immune system is producing too much of the antibody; it can also indicate the disease is more active and severe. However, not everyone with RA tests positive for the antibody, and some healthy people can have high blood levels with no presence of disease.
Anti-CCP antibody: CCP stands for cyclic citrullinated peptide, an antibody that binds to the amino acid citrulline, which is present in most people with RA. A positive anti-CCP may indicate the disease is more likely to progress quickly and increase the risk of joint damage. Combined with the RF test, it’s the best predictor of aggressive RA.
Antinuclear antibodies (ANA): These are antibodies that often signal an autoimmune disease. They appear in up to 40% of people with RA. Testing for ANA may also help rule out other diseases such as lupus and Sjögren’s syndrome.
Erythrocyte sedimentation rate (ESR): This is often called your “sed” rate; it measures how quickly red blood cells clump together, fall and settle (like sediment) in a test tube. A high ESR indicates more inflammation and more disease activity. This test can be used to diagnose RA, measure disease progression and also monitor how well you’re responding to treatment.
C-reactive protein: High levels of this protein signal inflammation and injury in the body. Like the ESR test, C-reactive protein levels are used to determine how active the disease is and how well you’re responding to treatment.
Red blood cell (RBC) count: A low RBC count can signal anemia, a common side effect of RA. However, anemia has many other causes in addition to RA. More severe anemia is often correlated with more severe disease activity.
White blood cell (WBC) count: A low WBC count can occur from a rare side effect of RA, Felty’s syndrome, which is characterized by repeated infections and an enlarged spleen.