hs-CRP
At a Glance
Why Get Tested?
May be used to predict your risk of developing heart disease
When to Get Tested?
When risk factors for heart and blood vessel disease are present as part of cardiac risk assessment; currently most testing is done in research settings
Sample Required?
A blood sample drawn from a vein in your arm.
Repeat testing is required as levels vary over time in individuals.
Test Preparation Needed?
None
The Test Sample
What is being tested?
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 drawn 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.
The Test
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 on the high end of the normal range, it may be a sign that you are at risk for 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 sign 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.
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).
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 difficult to implement in practice because of the need to be tested on several occasions.
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?
Relatively few Australian laboratories perform the hs-CRP currently and not all labs have the ability to do it.
Taking aspirin or statins (cholesterol-lowering drugs) may reduce CRP levels in blood. Both aspirin and statins 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 CRP levels.
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 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, should not have hs-CRP levels measured because their results can’t be considered in the context of heart disease. Their CRP levels would be very high - too high for hs-CRP to be measured meaningfully.
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