A blood sample taken from a vein in your arm
C-reactive protein (CRP) is a protein in the blood that increases when inflammation is present. CRP has been used for many years as an indicator of infection and inflammation associated with disease. Doctors now believe that atherosclerosis (fatty build-up in artery walls, also called 'hardening of the arteries') is also an inflammatory process. However, the inflammation from atherosclerosis is a low level of long-term inflammation that produces only small amounts of CRP. Therefore, the test requires higher sensitivity than previous tests in order to detect the small increases of CRP. Thus, this test is known as high-sensitivity CRP or hs-CRP.
How is the sample collected for testing?
A blood sample is taken by needle from a vein in your arm.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
hs-CRP is being proposed as a method for predicting a healthy person’s risk of heart attack or other heart conditions.
If your hs-CRP level is at the high end of the normal range, it may suggest that you are at risk of developing cardiovascular (heart and blood vessel) disease and other heart conditions. People who seem to be healthy but who have hs-CRP results in the highest quarter of test results have 2 to 4 times the risk of developing blocked arteries, compared with those in the lowest quarter.
The CRP molecule itself is not a harmful molecule in the body. The higher level of CRP is simply a marker of higher than normal inflammation. Because half of heart attacks and strokes happen in patients who do not have high levels of fat in their blood, measurement of hs-CRP may help doctors identify patients who are at risk and may need medical treatment to reduce your risk of developing vascular disease.
When is it requested?
Unfortunately, there is no agreement about exactly when the test should be used, and who should have this test. There is not yet a consensus about its value, but the test is being promoted by some as a test to help cardiologists assess risk for acute coronary syndrome (clogged blood vessels around the heart). Some doctors use the test to assist with making the decision whether to prescribe lipid lowering medication to reduce vascular risk. Where the decision has already been made to commence lipid lowering treatment, there may be little to be gained by measuring hs-CRP.
hs-CRP is usually requested as one of several tests for a cardiovascular risk profile, often along with lipid (fat) tests, like the various tests for cholesterol and triglycerides. Some experts say that the best way to predict risk is to combine a good marker for inflammation, like CRP, along with the ratio of total cholesterol to HDL cholesterol.
Currently there are no official guidelines on using hs-CRP as a test in screening for cardiovascular risk. Recent studies have shown, however, that the hs-CRP test may be useful in identifying risk in healthy individuals as well as in people who have symptoms of chest pain. This is not current UK practice.
What does the test result mean?
The results are generally interpreted on a relative scale. People with the highest values have the highest risk of heart disease and those with the lowest values have the lowest risk. This is often expressed in quintiles (five divisions) with those in the top fifth (the highest 20%) having risk of heart disease about twice that of those in the bottom fifth (lowest 20%).
Is there anything else I should know?
Currently, relatively few UK laboratories perform the hs-CRP blood test and not all laboratories have the ability to do it.
Taking aspirin or pravastatin (a cholesterol-lowering drug) may reduce CRP levels in blood. Both aspirin and pravastatin may help to reduce the inflammation linked to the atherosclerotic process. Other drugs, such as nonsteroidal-antiinflammatory drugs (for example ibuprofen) and glucocorticoid drugs, may also lower the concentration of CRP in the bloodstream.
Because hs-CRP tests measure a marker for inflammation, doctors need to know about recent medical events that may also have increased CRP levels, such as recent surgery, tissue injury, infections, or general inflammation, from conditions like arthritis.
hs-CRP and CRP tests measure levels of the same molecule. The hs-CRP test is designed to measure lower levels of the molecule. People with inflammation, such as those with arthritis or infections should not have hs-CRP levels measured because their results cannot be considered in the context of heart disease. Their CRP levels would be very high—too high for hs-CRP to be measured meaningfully.
I feel fine. Why do I need to take tests like hs-CRP for heart disease?
I have had cholesterol tests, but never an hs-CRP test. Why?
The hs-CRP test is fairly new, and many UK laboratories don’t perform this test yet. Experts still don’t agree on how often this test should be requested for a healthy population.
What is the difference between regular CRP and hs-CRP tests?