Rheumtology blood tests
of a blood sample can provide important information about rheumatologic
conditions, which are marked by inflammation in the joints, muscles,
connective tissues, and other structures. The following blood
tests are commonly performed to detect or evaluate rheumatologic
disorders, including rheumatoid arthritis (RA), systemic lupus
erythematosus (SLE), scleroderma, blood vessel inflammation (vasculitis),
tests for autoimmune disorders are often necessary. Many rheumatologic
conditions including RA, SLE, and sclerodermaare
caused by an abnormal autoimmune response where the body mistakenly
releases immune cells to attack healthy tissues.
blood counta general test that measures the amounts of
various blood cellscan provide clues to the presence of
inflammation, which tends to increase levels of white blood cells
and platelets and decrease the amount of red blood cells.
chemistry screen is another general test that can help to identify
problems in the bodys organs, especially the kidneys. Certain
types of inflammatory arthritis, including RA, can affect kidney
function, as can certain arthritis drugs.
sedimentation rate (ESR) refers to the rate at which red blood
cells, or erythrocytes, settle at the bottom of a test tube to
form a sediment. The ESR is increased in many rheumatologic disorders,
particularly those associated with vasculitis.
factor, a type of antibody present in the blood of many individuals
with RA, is thought to play a major role in the tissue destruction
associated with this disease. About 80% of patients with RA test
positive for rheumatoid factor, so this test is considered extremely
useful for confirming a diagnosis of this type of arthritis.
acid is the final breakdown product of purinesthe building
blocks of RNA and DNA. The blood test for this substance is primarily
used to detect gout, a form of arthritis that typically affects
the joints of the feet and hands. Uric acid levels may also be
elevated in some kidney disorders and other conditions that are
associated with excessive tissue destruction.
Purpose of the Test
and monitor rheumatologic and autoimmune disorders.
Who Performs It
A doctor, a
nurse, or a lab technician draws the blood sample.
As many as
25% of healthy elderly people have slightly elevated rheumatoid
factor levels, and the antibody may also be produced as a result
of chronic inflammation unrelated to RA, certain infectious disorders,
and certain other diseases.
to rheumatologic disorders, various other factors may affect
ESR values, including age, menstruation and pregnancy, anemia,
kidney disease, thyroid disease, certain infections, hormone
disorders, cancer, and certain medications and vitamins.
Uric acid levels
may be elevated due to starvation, stress, alcohol abuse, and
increased intake of high-purine foods (such as liver, kidney,
sweetbreads, and anchovies). Certain medications and vitamins
may also alter the test results.
Before the Test
Report to your
doctor any medications, vitamins, or supplements you are taking.
You may be advised to discontinue certain of these agents before
You must fast
for 8 hours before a blood test for uric acid.
What You Experience
A sample of
your blood is drawn from a vein, usually in your arm, and sent
to a laboratory for analysis.
Risks and Complications
After the Test
after blood is drawn, pressure is applied (with cotton or gauze)
to the puncture site.
normal diet and any medications withheld before the test.
Blood may collect
and clot under the skin (hematoma) at the puncture site; this
is harmless and will resolve on its own. For a large hematoma
that causes swelling and discomfort, apply ice initially; after
24 hours, use warm, moist compresses to help dissolve the clotted
sample is sent to a laboratory for analysis. A physician will
review the results for evidence of a rheumatologic disorder.
If an abnormality
is found and your doctor can make a definitive diagnosis, appropriate
treatment will begin.
In many cases,
abnormal results on one or more of these blood tests may necessitate
additional procedures, such as joint or muscle biopsy, to establish
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