Blood Tests For Rheumatoid Arthritis

What blood test determines a rheumatoid arthritis diagnosis? Is there any one blood test that indicates an accurate diagnosis? While there is no one blood test that accurately diagnoses rheumatoid arthritis, there are several blood tests when used in combination with examinations help to distinguish rheumatoid arthritis from other forms of arthritis and other rheumatic diseases.

A complete blood count (CBC) test is ordered for general information related to inflammation and anemia as well as an erythrocyte sedimentation rate (ESR) test.

The erythrocyte sedimentation rate (ESR) or "sedrate" test measures the rate at which red blood cells fall in a tube. Inflammation causes proteins to be present in the blood which makes the red blood cells clump together and settle more quickly to the bottom of the tube. Thus the higher the rate of sedimentation the greater the amount of inflammation. This test measures inflammation of any kind and therefore does not alone serve as a test for rheumatoid arthritis. It is a useful diagnostic for detecting the effects of treatment since inflammation should decrease as the disease is brought under control.

C-Reactive Protein (CRP) measures a protein that is present in the blood manufactured by the liver when acute inflammation is present. This test also serves well as a monitoring tool for the effects of the medication or the presence of a rheumatoid arthritis flare-up.

The rheumatoid factor (RF) test was discovered in the 1940s. This test is used to detect the presence of the rheumatoid factor anti-body which is present in 80% of cases of rheumatoid arthritis. The test is not conclusive and may indicate other rheumatoid diseases or may not show as seropositive in some rheumatoid arthritis cases. It often takes many months to appear in the blood and may show as seronegative in the early stages. However, when present in combination with other factors, the level of rheumatoid factor indicates the severity of the rheumatoid arthritis.

The anti-CCP (anti-cyclic citrullinated peptide antibody) test is a new and useful test especially in early diagnosis of rheumatoid arthritis. Research comparing the results of the anti-CCP test with the RF test and the ANA test shows that a positive result for this test practically confirms the rheumatoid arthritis diagnosis.

The antinuclear antibody (ANA) test is used to test for certain rheumatic diseases. The presence of this antibody indicates a diagnosis of Lupus, a related disease to rheumatoid arthritis. This test is often ordered to aid in the diagnosis of rheumatoid arthritis by eliminating the diagnosis of Lupus if not present. Some rheumatoid arthritis patients do test positive for ANA so other criteria is needed as well to get an accurate diagnosis of RA.

Anti-DNA and Anti-Sm tests are used to diagnosis Lupus since it is unusual to find antibodies to DNA (deoxyribonucleic acid) in anyone who does not have Lupus. Since Lupus is a similar disease to rheumatoid arthritis, this test aids as a distinguishing diagnosis between the two diseases.

While this list is not a complete list of all blood tests used in a rheumatoid arthritis diagnosis, it covers the major tests used today. The results should be interpreted in light of a complete examination including the specifics of the joints being affected.