Blood Test: C-Reactive Protein (CRP)
Blood Test: C-Reactive Protein (CRP)What It Is
A C-reactive protein (CRP) blood test is used to identify inflammation or infection in the body.
C-reactive protein is released into the blood by the liver shortly
after the start of an infection or inflammation. CRP is an early
indicator of these problems because its levels usually start to rise in
the blood before symptoms, such as fever and pain, appear.Why It's Done
Doctors may order the C-reactive protein test if symptoms suggest any
kind of inflammation, particularly related to inflammatory bowel
disease (IBD), arthritis flare-ups, or an autoimmune disorder such as
rheumatoid arthritis or lupus.
It may also be used to detect infections in vulnerable patients, such
as those who've just had surgery. The CRP test also may help determine
whether treatment for any of these conditions is working, because CRP
levels drop quickly as inflammation subsides.Preparation
No special preparations are needed for this test. Make sure to tell
your doctor about any medications your child is taking because certain
drugs might alter the test results.
On the day of the test, having your child wear a short-sleeve shirt
can make things easier for your child and the technician who will be
drawing the blood.The Procedure
A health professional will usually draw the blood from a vein. For an
infant, the blood may be obtained by puncturing the heel with a small
needle (lancet). If the blood is being drawn from a vein, the skin
surface is cleaned with antiseptic, and an elastic band (tourniquet) is
placed around the upper arm to apply pressure and cause the veins to
swell with blood. A needle is inserted into a vein (usually in the arm
inside of the elbow or on the back of the hand) and blood is withdrawn
and collected in a vial or syringe.
After the procedure, the elastic band is removed. Once the blood has
been collected, the needle is removed and the area is covered with
cotton or a bandage to stop the bleeding. Collecting blood for this test
will only take a few minutes.What to Expect
Either method (heel or vein withdrawal) of collecting a sample of
blood is only temporarily uncomfortable and can feel like a quick
pinprick. Afterward, there may be some mild bruising, which should go
away in a few days.Getting the Results
The blood sample will be processed by a machine. The results are commonly available after a few hours or the next day.
Generally, an elevated CRP level indicates an infection or
inflammation somewhere in the body. But the CRP alone can't tell doctors
where the problem is or what's causing it, so further testing may be
The C-reactive protein test is considered a safe procedure. However,
as with many medical tests, some problems can occur with having blood
drawn, such as:
Helping Your Child
- fainting or feeling lightheaded
- hematoma (blood accumulating under the skin causing a lump or bruise)
- pain associated with multiple punctures to locate a vein
Having a blood test is relatively painless. Still, many kids are
afraid of needles. Explaining the test in terms your child can
understand might help ease some of the fear.
Allow your child to ask the technician any questions he or she might
have. Tell your child to try to relax and stay still during the
procedure, as tensing muscles and moving can make it harder and more
painful to draw blood. It also may help if your child looks away when
the needle is being inserted into the skin.If You Have Questions
If you have questions about the C-reactive protein test, speak with your doctor.