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New Blood Tests Show Greater Hope for Detecting Heart Disease

September 11, 2000|From Washington Post

Just as new imaging techniques are emerging, so are new blood tests that could better pinpoint heart disease risk. None of these are ready for wide application, according to an extensive review published earlier this year by the Prevention Conference V, a panel of experts convened by the American Heart Assn. But each shows promise and is the subject of much study. Here are the most interesting new cardiac tests, plus information about the current standard cholesterol tests:

C-Reactive Protein (CRP): Scientific evidence has suggested that inflammation somehow plays a role in the formation of arterial blockages and the development of heart disease. The trick is to find a test that could measure inflammation in the arteries and blood vessels of individual patients. That's where C-reactive protein comes in. It's a sensitive marker for vascular inflammation, which may set the stage for accumulation of atherosclerotic plaque.

Several prospective studies have shown that CRP tests can predict future heart attacks, and they could prove to be a valuable addition to cholesterol tests and other blood analyses now performed to assess cardiovascular risk. A commercial CRP test is in the works and expected to be available soon, according to the AHA's Prevention Conference V group, which stopped short of recommending its use for the general public until more studies are completed.

Homocysteine: This amino acid--a building block of proteins in the body--is essential for good health. But levels of homocysteine that are too high appear to raise both blood cholesterol levels and the risk of heart disease.

Prevention V nixed routine measurement of homocysteine for now because of a lack of standardization and inconsistent results in studies that tried to predict future heart attacks and strokes based on homocysteine levels. But it did advise two uses of homocysteine testing. One was for people who have coronary heart disease but no other risk factors, such as high blood pressure or diabetes. The other was to screen people with a strong family history of heart disease but in whom other risk factors such as elevated blood cholesterol levels could not be identified. If homocysteine levels are elevated in these patients, Prevention V recommended, they should consume at least the recommended dietary allowance of folic acid, a vitamin that has been linked to protective heart benefits.

Lipoprotein (a), or Lp(a): "LP-little-A" is a fat-protein molecule that gloms onto various fats and whisks them through the blood. While Prevention V found it to be a promising new marker of cardiovascular risk, Lp(a) suffers from the same lack of measurement standardization and lack of consistent results in predicting future cardiac events that keep homocysteine from being routinely used.

Cholesterol: It's not experimental, but this is the gold standard of blood tests for heart disease risk.

The reason? Cholesterol, a waxy substance produced by the liver and found in foods derived from animals, is the main component of atherosclerotic plaque. Total blood cholesterol levels should not go above 200 milligrams per deciliter, according to the National Heart, Lung and Blood Institute. What also counts are levels of the detrimental low-density lipoprotein (LDL) and amounts of the protective high-density lipoprotein (HDL). Both are components of cholesterol.

Many doctors, including Alan Wasserman, chairman of medicine at George Washington University Medical Center, are getting even more aggressive about lowering blood cholesterol levels in people at high risk. "If there are known coronary disease or even significant risk factors--family history is the most significant--then LDL should be close to 100 milligrams," Wasserman says.

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