How is it used?When is it ordered?What does the test result mean?Is there anything else I should know?
There are two different tests for CRP. The
standard test measures a much wider range of CRP levels but is less
sensitive in the lower ranges. The hs-CRP test can more accurately detect lower concentrations of the protein (it is more sensitive), which makes it more useful than the CRP test in predicting a
healthy person's risk for
cardiovascular disease.
hs-CRP is promoted by some as a test for determining the potential risk level for cardiovascular disease, heart attacks, and strokes. The current thinking is that hs-CRP can play a role in the evaluation process before one encounters one of these health problems. More clinical trials that involve measuring hs-CRP levels are currently underway in an effort to better understand its role in cardiovascular events and may eventually lead to guidelines on its use in screening and treatment decisions.
hs-CRP usually is ordered as one of several tests in a cardiovascular risk profile, often along with tests for
cholesterol and
triglycerides. Some experts say that the best way to predict risk is to combine a good marker for inflammation, like hs-CRP, along with the
lipid profile.
What does the test result mean?NOTE: This test has no single number that identifies an abnormal result.
Your lab report (see a sample report) should include
a range of numbers (reference range) that identifies what is expected for you based on
your age, sex, and the method used in that laboratory. You can find more information
about expected results at Reference Ranges
and What They Mean. Lab Tests Online strongly recommends that you discuss the meaning of your test results with your doctor.
People with higher hs-CRP values have the highest risk of
cardiovascular disease, and those with lower values have less of a risk. Specifically, individuals who have hs-CRP results in the high end of the normal range have 1.5 to 4 times the risk of having a
heart attack as those with hs-CRP values at the low end of the normal range.
The American Heart Association and US Centers for Disease Control and Prevention have defined risk groups as follows:
- Low risk: less than 1.0 mg/L
- Average risk: 1.0 to 3.0 mg/L
- High risk: above 3.0 mg/L
These values are only a part of the total evaluation process for cardiovascular diseases. Additional risk factors to be considered are elevated levels of cholesterol, LDL-C, triglycerides, and glucose. In addition, smoking, having high blood pressure (hypertension), and being diabetic also increase the risk level.
Is there anything else I should know?
Taking nonsteroidal anti-inflammatory drugs ((NSAIDs like aspirin, ibuprofen, and naproxen) or
statins may reduce CRP levels in blood. Both anti-inflammatory drugs and statins may help to reduce the
inflammation, thus reducing CRP.
Because the hs-CRP test can serve as a marker for inflammation, it is important that any person having this test be in a healthy state in order for the results to be of any value in predicting the risk of coronary disease or heart attack. Any recent illness, tissue injury, infection, or other general inflammation will raise the amount of CRP and give a falsely elevated estimate of risk.
Women on hormone replacement therapy have been shown to have elevated hs-CRP levels, suggesting that this test may be useful in predicting future cardiovascular events.
Since the hs-CRP and CRP tests measure the same molecule, people with chronic inflammation, such as those with arthritis, should not have hs-CRP levels measured. Their CRP levels will be very high due to the arthritis—often too high to be measured or meaningful using the hs-CRP test.
