FRIDAY, Feb. 20, 2004 (HealthDayNews) -- Just when patients were getting comfortable with the concept of "good" and "bad" cholesterol levels, doctors are readying another kind of heart-health test.
The good news, according to some experts, is that the so-called ApoB test is an even better way to figure out if your arteries are in danger of clogging.
There are a few caveats, says Dr. Gerald S. Berenson, a professor of medicine at Tulane University in New Orleans. ApoB tests are more expensive than traditional cholesterol tests. And researchers haven't developed firm guidelines on how to interpret them. Even so, it's "very valuable" for doctors to test the ApoB levels of their patients, he says.
Just as constricted water hoses burst under pressure, blocked arteries can rupture, leading to a heart attack or stroke. For decades, doctors have relied on cholesterol tests to determine whether people are at risk of developing atherosclerosis, also known as hardening of the arteries.
The problem is that traditional cholesterol tests only provide part of the picture of what's going on inside arteries, says Dr. Steven Haffner, a professor of medicine at the University of Texas Health Science Center in San Antonio. In essence, cholesterol tests only measure the number of leaves on trees in a forest, not the total number of trees, which is more important, he says.
In a study released last October in the journal Circulation, Haffner and his colleagues reported that blood levels of apolipoprotein B (ApoB) appear to be a better measure of heart disease risk than normal LDL ("bad") cholesterol levels. That study examined the results of blood tests and compared them to other measures of heart risk among 1,522 patients.
ApoB tests measure a component of LDL cholesterol, "the stuff that gets into the arterial wall as part of the atherosclerosis process," Berenson says.
"It is a better predictor in general" of heart disease, and could reveal problems in patients who have normal cholesterol levels, Haffner says.
ApoB also appears to be more related to potential risks factors such as insulin resistance than traditional LDL cholesterol, Haffner says. If patients have high ApoB levels, they can lower them by taking statin drugs, the same medications that are used to lower cholesterol.
ApoB tests are not yet routine, however. Haffner says they can be useful in patients at high risk of heart disease.
But at least one doctor isn't quite ready to embrace ApoB tests.
It's true that LDL cholesterol levels can miss the full threat of clogged arteries, says Dr. Alistair Fyfe, chief of cardiology at Medical City Dallas Hospital. But ApoB tests don't do a much better job, he says, because they can't pinpoint how much cholesterol is floating around. Other types of new tests can measure the size of cholesterol particles and will make ApoB tests "obsolete," he says.
When the costs of these particle-size tests become reasonable, they "will wipe everything else off the map," Fyfe says. He adds that other tests will also give doctors a better handle on which drugs to use.
Berenson says both kinds of tests -- those that measure ApoB levels and particle sizes -- are important, but the ApoB tests remain much cheaper. By combining traditional cholesterol tests with ApoB tests, he says, doctors can still get an "excellent measure" of what's going on in your arteries.
To learn more about ApoB testing, visit the University of California, San Francisco. Get the lowdown on cholesterol figures from the National Heart, Lung, and Blood Institute or the American Heart Association.