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updated 1/12/2011 6:59:35 PM ET 2011-01-12T23:59:35

Health experts have touted the heart benefits of keeping our levels of "bad" LDL cholesterol low, and our levels of "good" HDL cholesterol high. But new research shows heart disease risk may be better assessed by measuring HDL's ability to remove artery-clogging plaque, rather than the HDL levels themselves.

The finding suggests there may be a protein or compound in some kinds of HDL cholesterol that is better at removing bad cholesterol than other kinds of HDL, said study researcher Dr. Daniel J. Rader, director of preventive cardiology at the University of Pennsylvania School of Medicine.

In other words, not all "good" cholesterol is equally healthy.

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While more research is needed to confirm this, Rader said, the study begins to explain why some people with high HDL levels have a high risk of heart disease, while others have low levels of HDL but are protected from heart disease.

"Why [does it] differ from person to person in terms of their HDL functionality? I think it probably is, in some way, related to the composition of their HDL," he told MyHealthNewsDaily.

The study will be published tomorrow (Jan. 13) in the New England Journal of Medicine.

Better HDL effectiveness, lower heart disease risk
Rader and his colleagues drew blood and measured HDL levels of 203 healthy people without heart problems, 442 patients with coronary artery disease who were having surgery, and 351 control patients also having surgery but who didn't have coronary artery disease.

Researchers also measured the thickness of their arterial walls (the thicker the walls, the higher the risk of heart disease).

They then isolated HDL cholesterol from the participants' blood, and tested the ability of the HDL to extract the cholesterol from the cells, which is called cholesterol efflux capacity.

Rader and his colleagues found that the HDL cholesterol from people who had  coronary artery disease didn't pump cholesterol out the cells as well as the HDL cholesterol from people without the disease.

Therefore, the risk of coronary artery disease decreased as HDL's ability to remove cholesterol increased, the researchers concluded.

And when it came to predicting heart disease, a patient's HDL levels were a less effective measure than the HDL's ability to remove cholesterol, the researchers said.

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Future tests
The test is too labor-intensive as it is to be used clinically, Rader said.

But "if we can find that there's a particular protein that's a major determinant" of how well HDL can remove bad cholesterol from cells, that would be a better way of testing HDL effectiveness in the future, he said.

This would be similar to how levels of C-reactive proteins are currently tested to determine the degree of inflammation in the body, he said.

A future test could make it easier to determine if someone with high HDL levels, but poor HDL function, is at an increased risk for heart disease, Rader said.

Pass it on: The ability of "good" HDL cholesterol to remove "bad" LDL cholesterol from arteries is a better predictor of heart disease than just measuring levels of HDL cholesterol in the blood.

Follow MyHealthNewsDaily staff writer Amanda Chan on Twitter @ AmandaLChan.

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