What is C-reactive
C-reactive protein (CRP)
is a substance produced by the liver in response to inflammation. Other names
for CRP are high-sensitivity C-reactive protein (hs-CRP) and ultra-sensitive
C-reactive protein (us-CRP).
A high level of CRP in the
blood is a marker of any condition that causes inflammation, from an upper
respiratory infection to cancer. High CRP levels can indicate that there is
inflammation in the arteries of the heart, which can mean a higher risk for
heart attack. It is important to remember, however, that CRP is an extremely nonspecific
test and can be elevated in any inflammatory condition.
What does it mean
to have a high CRP?
Doctors don’t all agree on
the implications of high CRP levels. Some believe there’s a correlation between
high CRP levels and an increased likelihood for heart attack or stroke.
The Physicians’ Health Study found that among nearly 15,000 healthy adult men,
a high level of CRP was associated with a risk of heart attack that was three
times higher than average. According to the Cleveland
Clinic, the Harvard Women’s
Health Study showed that high CRP levels were more predictive of coronary
conditions in women than were high cholesterol levels. High cholesterol is a
more commonly cited risk factor.The Jackson Heart Study found that hs-CRP is associated with type 2 diabetes in African-Americans.
Doctors may order this
test in conjunction with other tests to assess a person’s risk for heart
disease or stroke. Doctors may also order a CRP test after surgery to check for
signs of postsurgical infection or to monitor inflammatory diseases, including:
arthritis such as rheumatoid
diseases, such as lupus
Who should receive
the C-reactive protein test?
According to the Mayo Clinic, the American Heart Association does not recommend
the test for general screening of heart disease. If
you are one of the 47 percent of Americans with risk factors for heart
disease, CRP test results might help you better monitor your heart health. The
Centers for Disease Control and Prevention (CDC) consider high blood pressure,
high cholesterol, and smoking as big risk factors for heart disease. If you
have a family history of heart disease, you are also at high risk.
No special preparation is
necessary for this test. You may eat normally on the day of the test. A nurse
or other health practitioner will draw blood from a vein, usually on the inside
of your elbow or the back of your hand.
First, they will clean the
skin over the vein with antiseptic. Next, they’ll wrap an elastic band around
your arm, causing your veins to bulge out slightly. Then, the practitioner will
insert a small needle into the vein and collect your blood in a sterile vial.
After the nurse or health
practitioner collects your blood sample, they will remove the elastic band
around your arm and ask you to apply pressure to the puncture site with gauze.
They may use tape or a bandage to hold the gauze in place.
Risks of a
C-reactive protein test
This is a routine test
with low risk, but there’s a slight chance of the following complications from
the blood draw:
- dizziness or
- bruising or
infection at the puncture site
A CRP test can be helpful
in assessing a patient’s risk of heart disease, especially in combination with
high cholesterol levels. The benefits of this test outweigh potential
complications, especially for those at risk for heart disease or stroke and
those recovering from recent surgery.
What do the test
C-reactive protein is
measured in milligrams of CRP per liter of blood (mg/L). In general, a low
C-reactive protein level is better than a high one, because it indicates less
inflammation in the body.
According to the Cleveland
Clinic, a reading of less
than 1 mg/L indicates you’re at low risk of cardiovascular disease. A reading
between 1 and 2.9 mg/L means you’re at intermediate risk. A reading greater
than 3 mg/L means you’re at high risk for cardiovascular disease. A reading
above 10 mg/L may indicate a need for further testing to determine the cause of
severe inflammation in your body.
An especially high CRP
reading of greater than 10 mg/L may indicate:
- a bone
infection, or osteomyelitis
- an arthritis
- lupus, another
connective tissue disease, or another autoimmune disease
Note that CRP levels may
also be high if you’re on birth control pills or in the second half of
pregnancy. Low-grade inflammation levels can be increased by both oral contraceptives and the increased blood flow that begins midway
through the second trimester of pregnancy.
If you are pregnant or
have any other chronic infection or inflammatory disease, a CRP test is
unlikely to accurately assess your risk for heart disease. Before having a CRP
test, speak to your doctor about any medical conditions that may skew the test
results. Since there are other blood tests that can be performed instead, you
might wish to forego a CRP test altogether.
Remember that this test
doesn’t provide a complete picture of your risk for cardiovascular disease.
Your doctor will consider your lifestyle risk factors and family history when
determining which follow-up tests are best for you. He or she may also order
tests such as an EKG, echocardiogram, stress test, CT scan of the coronary
arteries, or heart catheterization.
should you do if you have high CRP?
Lowering your CRP is not a
guaranteed way to lower your risk of cardiovascular, kidney, or autoimmune
disease. It’s important to know that high CRP is what doctors call a “biomarker.”
A biomarker is a factor to keep in mind when analyzing a person’s health, but
not a standalone indicator of a particular diagnosis.
review of the medical literature indicates that a healthy dietary pattern resulted in lowered CRP
levels. The Mediterranean diet and the Nordic diet were both linked to a
decrease in CRP. If you are at risk for heart disease, pursuing a healthy diet
that works for you should be part of your lifestyle regardless.
If you are at high risk
for cardiovascular disease and your test results show high CRP, your doctor may
suggest a statin or other cholesterol-lowering medication. An aspirin regimen
may be recommended as well. Vitamin C has also been explored as an effective treatment to lower CRP levels for
people that are at an elevated risk for cardiovascular disease.