Test for Protein Called ApoB Better Measure of Heart Attack, Stroke Risk
By Salynn Boyles
WebMD Medical News
Reviewed by Elizabeth Klodas, MD
March 27, 2008 -- People at high risk for heart attacks and strokes may need even more aggressive cholesterol control than is currently recommended, experts now say.
In a joint statement released Thursday by the American Diabetes Association (ADA) and the American College of Cardiology (ACC), the experts concluded that measuring LDL, or bad, cholesterol may no longer be the best measure of heart health in these patients.
The panel found that once LDL cholesterol is lowered to recommended levels in high-risk patients, testing for the protein ApoB may more accurately identify those still at risk for cardiovascular events.
If ApoB levels are high, patients may need more aggressive lifestyle interventions or larger doses of lipid-lowering statin drugs, even if LDL cholesterol levels are within normal range, the panel concluded.
"LDL measurement is still very important," ADA Vice President of Clinical Affairs Sue Kirkman, MD, tells WebMD. "But for high-risk people who are on statin therapy it may not be enough to get LDL down below 100 or even 70."
LDL and ApoB
Achieving an LDL of below 100 milligrams/deciliter is now widely recommended for patients with two or more risk factors for heart disease and for those with diabetes but no other major heart disease risk factors.
Guidelines call for a target LDL at or below 70 for patients with established heart disease or diabetes with additional risk factors for heart disease.
These risk factors include high blood pressure, tobacco use, and family history of heart disease.
While aggressive cholesterol treatment has contributed to reductions in heart attacks and strokes, these events are still common among high-risk patients who reach the target goals, Kirkman says. This could occur if other cholesterol particles that contribute to risk are still elevated.
ApoB is a molecule that is present in all the cholesterol particles that significantly contribute to the development of atherosclerosis (also known as plaque or hardening of the arteries). The hope is that measuring ApoB will help patients and their doctors better gauge actual risk because ApoB will be a more accurate measure of the total number of all artery-clogging particles (not just LDL). There is growing evidence that ApoB levels are a better indicator of heart risk than total cholesterol or LDL.
For this reason, the joint panel recommends a target ApoB level of less than 90 for high-risk patients without established heart disease and less than 80 for the highest-risk patients with heart disease or with diabetes and other cardiovascular risk factors.
Statins and Lifestyle
The report could lead to more aggressive treatment of high-risk patients with lipid-lowering statins, but the panel concluded that more research is needed to confirm the benefits of this approach.
The group also called for public health initiatives aimed at promoting lifestyle changes that reduce cardiovascular risk.
Kirkman says patients and their doctors often focus on drug treatments, forgetting that lifestyle changes can also have a big impact on risk.
"It is important to remember that lifestyle is a big part of this," Kirkman says. "Getting patients to improve their diets, stop smoking, and exercise are all critical. It isn't all about drugs."