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
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
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
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.