How is it used?
hs-CRP is being proposed as a method for predicting a healthy person’s individual risk of a 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 . Because half of heart attacks and strokes happen in patients who do not have elevated levels of cholesterol, measurement of hs-CRP may help doctors identify patients who are at increased risk and therefore may benefit from medical treatment.
When is it requested?
Currently, 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 some guidelines that recommend using hs-CRP as a test in screening for cardiovascular risk in certain groups of patients. 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 anti-inflammatory drugs (for example ibuprofen) and glucocorticoid drugs, may also lower CRP levels.
As hs-CRP tests measure a marker for inflammation, it is important that any person having this test be in a healthy state for the results to be of value in predicting the risk of coronary disease. Doctors need to know about recent medical events that may also have increased CRP levels, such as tissue injury, infections, or chronic inflammation (e.g. 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 chronic inflammation, such as those with arthritis and some other chronic illnesses e.g. inflammatory bowel disease and other autoimmune diseases, 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.