Blood Tests for Rheumatoid Arthritis

When you have rheumatoid arthritis (RA), your blood may show certain signs. Your doctor will look for these signs, or markers, when trying to diagnose you with RA. These markers also help rule out other autoimmune or inflammatory conditions.^1,2

If your doctor suspects RA, they will order a few blood tests. Many of these tests are also used to observe how your RA is progressing. Common tests are:^1,2

• Rheumatoid factor (RF)
• Anti-cyclic citrullinated peptide (anti-CCP) antibody
• Complete blood count (CBC)
• Erythrocyte sedimentation rate (sed rate or ESR)
• C-reactive protein (CRP)

Some of these tests measure antibodies. These are proteins that are part of the immune system. When antibodies are working correctly, they destroy germs by sticking to germs like:³

• Viruses
• Bacteria
• Fungi

When antibodies work differently than they should, they damage healthy tissue instead of germs.³

Your doctor may also run tests to check:²

• Your electrolyte levels
• Your muscle health
• How well your organs are working, including your:
  • Kidneys
  • Thyroid
  • Liver

RF

An RF blood test measures the RF antibody. This is a protein that people with RA may have in their blood. But RF can also appear in the blood of those with other types of autoimmune conditions. This is why a high RF level is not enough to diagnose RA. Also, some people with RA may test negative for RF.^2,4

Your RF levels may help your doctor decide which RA drug will work best for you. A high level of RF may help predict how severe your RA will be. It can also help predict what other conditions you may develop as your RA progresses.⁵

Anti-CCP

Another marker that people with RA often have in their blood is the anti-CCP antibody (ACPA). Anti-CCP may help your doctor diagnose RA early. This is because it appears in many people before RA symptoms occur. Between 6 and 8 in 10 people with RA have ACPAs.^2,4

The results of this test, along with the RF levels, are useful in confirming an RA diagnosis and the severity of your RA.^2,4

CBC

The CBC test measures:⁴

• Blood cell counts
• Levels of other important chemicals in the blood

This test can help diagnose anemia. This is a condition of low red blood cell count that many people with RA have.⁴

Sed rate

Sed rate, or ESR, measures how much inflammation is in your body. This test sees how quickly red blood cells (erythrocytes) separate from other cells and collect in the bottom of a test tube. Since inflammation can be caused by many conditions, this test is used with other tests to diagnose RA.⁴

Sed rate can also help check disease progress and your response to RA treatment.²

CRP

The CRP test is another test for inflammation. It measures CRP, a chemical found in the liver. High levels of CRP are common in:^2,4

• RA
• Other forms of arthritis
• Other conditions

Antinuclear antibody (ANA) test

The ANA test looks for antinuclear antibodies (ANAs). ANAs may indicate you have an autoimmune condition such as RA.⁴

Other blood tests for RA

Doctors are researching whether other tests can give a more accurate and early diagnosis of RA. These newer tests may also help get an earlier diagnosis for the 1 in 4 to 1 in 5 people who have RA but are seronegative. This means that they tested negative for RF and anti-CCP. Diagnosing RA sooner can help prevent joint damage and disability.⁶

These tests include:⁶

• Anti-mutated citrullinated vimentin (anti-MCV): This is another antibody test.
• Serum 14-3-3 eta: This is a protein that may be present in people with seronegative RA.
• Anti-carbamylated proteins (anti-CarP): This is another antibody test.

Some doctors may order a multi-biomarker disease activity (MBDA) test. But there is still debate about how useful this test may be in diagnosing RA.⁶