Who is likely to suffer a heart attack in their twenties or thirties? University of Texas researchers think they are a step closer to answering that question with the development of a simple, new blood test.

An estimated 1.5 million Americans suffer heart attacks each year, the American Heart Association reports. Some 75,000 of these victims -- about 5 percent -- are less than 40 years old. Physicians have been at a loss to pinpoint who these people will be.

The new blood test, developed by Dr. Jennifer Cuthbert and her colleagues at the University of Texas Health Sciences Center in Dallas, could change that.

Called the LDL receptor test, it can identify the one in 500 people likely to have a heart attack before middle age because of a genetic disease called familial hypercholesterolemia (FH). An estimated 400,000 Americans have FH. The disease produces an abnormally high blood level of the cholesterol fragment known as LDL, low-density lipoprotein. FH sufferers lack the normal means to remove LDL from the blood. This excess cholesterol blocks arteries and leads to a heart attack.

The test will enable researchers to "screen young people who have high cholesterol levels or family histories of heart attacks at an early age," Cuthbert says. "If we identify people with FH while they are young, with specific treatment we may be able to prevent heart disease later on."