updated 9/7/2004 5:55:33 PM ET 2004-09-07T21:55:33

A simple test that scrutinizes bad cholesterol more closely may more reliably predict who is going to have a heart attack, new research indicates.

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The current test measures total cholesterol and the breakdown of good HDL and bad LDL cholesterol. The new test, discussed Tuesday at the annual meeting of the European Society of Cardiology, instead measures the ratio of bad LDL cholesterol particles to good HDL cholesterol particles.

The smaller bad particles are called apolipoprotein B molecules and the good ones are called apolipoprotein A1 molecules. A ratio of 1 to 2 is considered low risk, while a ratio approaching 1 to 1 would be considered high risk, and anything over that — where the small LDL particles would dominate — would be very high risk.

If the LDL is mostly made up of small particles, that’s bad because they are dense and are the building blocks of plaque. The big ones are more easily carried away by the blood flow.

High ratio a key risk factor
The test was used in a major study investigating what causes heart attacks because researchers suspected it might be a better predictor of heart trouble than standard cholesterol tests.

The study followed 29,000 people in 52 countries. It compared 15,000 who had suffered a first heart attack with someone of the same age, sex and location who had not had a heart attack.

It found the standard cholesterol test did not correlate well with heart attacks, but that the new method was a better indicator. A high ratio of small LDL molecules to good cholesterol turned out to be the most important factor linked to heart attack risk, before even smoking.

Patients with the worst test results were about four times more likely than those with the best score to have a heart attack.

“Globally, 50 percent of the risk of a heart attack is predicted by the apo B/apo A1 ratio,” said the study’s leader, Dr. Salim Yusef, a professor of medicine at McMaster University in Canada.

“I was impressed,” said Dr. David Wood, a cardiologist at Charring Cross Hospital in London who was not connected with the research. “It made a significant independent contribution to risk prediction which was better than the other risk markers.”

However, Wood said it is too early to tell whether the new test will supplant the standard cholesterol test in the near future because it has been a struggle to get doctors to routinely test for cholesterol, even with the method that has been around for at least a decade.

“At the moment, the real challenge is to get doctors to measure lipids at all, in order to assess risk, and to manage patients to the goals of both total and LDL cholesterol,” he said. “If we can improve risk prediction by the ratio of apo-B to apo-A1, that is going to help in targeting treatment to the right patients, and that would be an improvement on what we’re doing now.”

Scientists believe genes determine an individual’s ratio of small to large LDL molecules and that only those with lots of small molecules would need to be put on cholesterol-lowering medication. Doctors are constantly searching for ways to better separate patients who would respond well to medication from those who either wouldn’t or don’t need it.

One of the main practical advantages of the new test is that blood can be drawn at any time. The current cholesterol test can only be done after the patient fasts for 12 hours. A machine then reads the cholesterol molecules and gives a ratio count.

Although the new test looks promising, said cardiologist Dr. Udo Sechtem, a professor at the University of Tuebinden in Stuttgart, Germany, it will take a mental adjustment, similar to getting people to convert to the metric system.

“It will take a lot of data and a lot of experience,” said Sechtem, who was not connected with the study.

© 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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