Should You Have Your CRP Measured?

Measuring CRP Can Be Important to Your Cardiac Health

Lab technician with blood samples and medical chart
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Measuring C-reactive protein (CRP) levels can be useful in assessing the risk of coronary artery disease (CAD) in some individuals. CRP is a protein that is released into the bloodstream during periods of inflammation. Since inflammation is now known to play a major part in the development of atherosclerosis (the process that forms plaques in the arteries), it makes sense that CRP levels might be elevated during periods of active plaque formation and that high levels of CRP would correlate with cardiovascular events.

Studies have now shown that elevated CRP is associated with an increased risk for cardiovascular events, such as heart attack and stroke. Whether CRP actually causes the increased risk or is just a marker for risk is still debated, though the preponderance of evidence suggests it is not a direct cause. Still, it is now known that treating people who have high CRP levels with statins can reduce their risk. This fact alone makes measuring CRP potentially worthwhile in some people.

How Is CRP Measured?

CRP is measured using a high sensitivity test (called the hs-CRP blood test). In general, the higher the hs-CRP level, the higher the risk. Levels of hs-CRP below 1 are considered low; levels of 1 - 3 are considered moderately elevated; levels greater than 3 are considered high. Levels greater than 10 are usually only seen with active, obvious inflammatory processes, such as severe infection, major trauma, or chronic inflammatory diseases - these ultra-high levels cannot be used to interpret cardiac risk.

Because CRP levels can fluctuate over time, most experts now recommend measuring 2 CRP levels a few weeks apart and averaging the two values.

Deciding whether measuring CRP should be part of the routine screening process has been difficult for two reasons. First, interpreting the significance of an elevated CRP level is often not straightforward, and can lead to more confusion rather than less.

Second, until recently it was unclear whether treatment should be changed in anybody based on the results of CRP values.

When Is It Useful To Measure CRP?

Elevated levels of CRP are most often associated with the presence of several other risk factors for cardiovascular disease such as smoking, obesity, sedentary lifestyle, increased cholesterol, hypertension and metabolic syndrome. So higher levels of CRP are usually seen in patients with the greatest number of additional risk factors. In these cases, finding a high CRP level merely confirms what already is quite apparent - the patient has a high risk of cardiac disease, and needs aggressive risk factor modification (most likely including statins) whatever their CRP levels.

On the other hand, an elevated CRP level in a person with only one or two other risk factors does add potentially important information. For these people, a high CRP level seems to indicate that their risk is higher than it otherwise appears.

It means that a little bit of hypertension, or a little bit of extra weight, is indeed associated with possible inflammation in the blood vessels and that the risk of cardiovascular events may be elevated. 

So, at the very least, having an elevated CRP level should make you and your doctor much more serious about risk reduction. Furthermore, data from the recent JUPITER study tells us that giving statins to apparently healthy patients who have high CRP levels can substantially and significantly reduce their risk of cardiovascular disease.

The bottom line

CRP levels certainly do not need to be measured in everybody. Before ever considering a CRP measurement, you and your doctor should assess your baseline risk of cardiac disease, based on the more obvious risk factors. This assessment will tell you whether you are in a high, intermediate, or low risk category.

If you are already in a high-risk category, measuring CRP will not be very helpful. You're reasonably likely to have a heart attack or stroke unless you aggressively reduce your risk, no matter what your CRP level may be. But if you or your doctor are hesitant to use statins, and are unsure of the benefit they may provide you, then measuring your CRP levels may give you one more reason to consider these risk-reducing drugs.

It is more reasonable to measure a CRP level if you are in the moderate risk category. An elevated CRP level here should send up the red flags that your risk is probably higher than you think. Also, if your cholesterol levels are normal or only a little elevated, then knowing that your CRP is high would give you and your doctor a clear-cut reason to consider therapy with statins.

With today's state of knowledge, the value of measuring CRP levels in people in the low-risk category is far less clear. If the CRP is elevated and you have no other risk factors, the use of statins could be considered but is very controversial. Most doctors agree that there is very little reason to measure CRP levels in people who are in the low-risk category.

If you do have your CRP measured and it comes back high, you may want to read this article: What To Do When Your CRP Is Elevated.


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