Sep292010

C-Reactive Protein Levels Vary by Race

by Howard LeWine, M.D.
Harvard Medical School

Levels of a blood protein linked to inflammation vary by race, a new study finds. The study looked at C-reactive protein (CRP). People with long-term high levels may be more likely to develop heart disease. Researchers reviewed 89 studies about CRP. They included more than 221,000 people. Researchers broke down CRP results for this large group by race. They found that blacks had the highest average level, 2.6 milligrams per liter (mg/L) of blood. Levels for Hispanics were nearly as high, 2.51. They were followed by South Asians (2.34) and whites (2.03). East Asians had the lowest levels, an average of 1.01. Some doctors look at CRP levels to help them decide when someone needs treatment with a statin drug. These drugs reduce LDL cholesterol and inflammation. They have been shown to reduce heart disease deaths. But researchers said their study shows that different races would be more or less likely to have "high" CRP. They said more study is needed to explain why. The study was in the journal Circulation: Cardiovascular Genetics. HealthDay news wrote about it September 28.

By Howard LeWine, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

CRP is short for C-reactive protein. It is a blood test that measures inflammation in the body. Inflammation can be caused an infection, such as pneumonia. A condition related to an overactive immune system, such as rheumatoid arthritis, also can cause inflammation. In these cases, there is a lot of inflammation. The level of CRP is often very high.

CRP also goes up if you have buildup of fatty deposits in your arteries. This is called atherosclerosis.

The laying down of fatty deposits in the arteries is a dynamic process. As the fat builds up in the artery wall, it damages the vessel's inner lining. The body tries to repair the damage by laying down a hard layer of the deposit. This constant damage-and-repair process leads to a long-term, low level of inflammation.

As a result, CRP rises with atherosclerosis. But the level is low compared with pneumonia, rheumatoid arthritis and other inflammatory conditions.

High CRP levels indicate an increased risk of heart disease. Researchers at Boston's Brigham and Women's Hospital have shown that this occurs even if LDL cholesterol levels are low. These researchers conducted a study called the JUPITER trial. They determined that reducing cholesterol with a powerful statin decreases the risk of heart attack and stroke in men over 50 and women over 60 who have a CRP of 2 milligrams per liter (mg/L) or higher.

To detect levels of CRP in this range requires a special test. Everyone in the study had an LDL cholesterol level of less than 130 milligrams per deciliter (mg/dL).

But apparently things are a bit more complicated than just using a CRP of 2 mg/L as a reason to take a statin. A new study shows that average CRP levels vary by race and ethnicity. The study is reported in the September 28 online issue of the journal Circulation: Cardiovascular Genetics.

On average, blacks have the highest CRP levels, at 2.6 mg/L, the study found. East Asians have the lowest, with an average of 1.0 mg/L. The average for whites is 2.0 mg/L. Should there be different "normal" CRP values for non-whites? That's not clear at this time.

What Changes Can I Make Now?

Doctors are still trying to decide when to order a CRP test and how to use the information. A higher than normal CRP is probably not an actual cause of heart disease and stroke. It is just one of the "markers" that indicate a higher than average risk. So lowering CRP with a statin drug may have nothing to do with decreasing the risk of heart and blood vessel disease. Statins decrease the risk in other ways, regardless of what happens to the blood level of CRP.

The factors that indicate an increased risk of heart disease and stroke are well established in medical practice. They provide enough guidance for the great majority of adults. So your first line of defense is to control these factors. How can you do this?

  • Avoid tobacco products.
  • Eat a Mediterranean-style diet.
  • Load up on fruits, vegetables and whole-grain foods.
  • Eat healthy sources of protein such as fish, nuts and beans.
  • Get regular exercise, according to your doctor's advice.
  • Keep blood pressure in the normal range.
  • Lower LDL cholesterol if it is too high.

Should all men over age 50 and all women over age 60 have a CRP blood level done, even if they have normal LDL cholesterol levels? My answer to this question is still no.

But the CRP blood test can be useful. Consider the case of someone who has one or more of the traditional risk factors for heart and blood vessel disease and an LDL cholesterol of less than 130 mg/dL. A high CRP result would mean more attention needs to be paid to diet and exercise. The person also should consider taking a statin drug to prevent a heart attack or stroke.

What Can I Expect Looking to the Future?

This new information about the variation in CRP by race and ethnicity definitely questions what should be considered a normal level for CRP.

But this is just one complicating factor in understanding how to use the CRP blood tests. In fact, there really is no true normal for CRP. Inflammation is an important and very normal reaction to any injury. It allows us to heal. Therefore CRP will and should go up and down.

The constant, low-grade inflammation in the arteries is what that concerns us. CRP is not a specific test for inflammation in the arteries. It is high when there is any inflammation, regardless of the cause. We will likely have a more specific test for inflammation in the arteries in the future.

Categories: Heart Health

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