Total Cholesterol, HDL Good Predictors of Heart Disease Risk
There's no added benefit to measuring other lipids, researchers say
TUESDAY, Aug. 14, 2007 (HealthDay News) -- Measuring total cholesterol and so-called "good" cholesterol or HDL is sufficient to predict heart disease risk without measuring other blood lipids, according to a new study.
Measuring other types of fatty substances in the blood -- substances called apolipoprotein B and A-I -- does not give any added value, said co-researcher Dr. Ramachandran S. Vasan, professor of medicine at Boston University School of Medicine.
"In the United States, [measuring] total cholesterol and HDL are part of the standard lipid profile," he said. But elsewhere, guidelines also recommend measuring apolipoprotein B and A-I and computing their ratio.
Apo B is the main protein component of low-density lipoprotein (LDL), the so-called "bad" cholesterol. A-I is the main component of HDL. Apo B proteins spur hardening of the arteries, while Apo A-I proteins protect against it.
Some research has suggested that measuring the ratio of Apo B and A-I might be superior to using the ratio of total cholesterol and HDL to figure out heart disease risk. So, Vasan and his colleagues decided to compare the two approaches to see if one was superior.
Their findings are published in the Aug. 15 issue of the Journal of the American Medical Association.
Vasan's team followed more than 3,300 middle-aged participants in the Framingham Offspring Study, a major study launched in 1971. Cholesterol measurements were taken in the years 1987 to 1991, when the men and women were free of heart disease.
After a follow-up of about 15 years, 291 participants, including 198 men, developed heart disease.
Measurements of the apo B to apo A-I ratio were compared with measuring the total cholesterol to HDL ratio to see how well each approach predicted the participants' heart disease.
The researchers concluded that the total cholesterol-to-HDL ratio was sufficient and that the other ratio does not substantially improve the accuracy of the prediction.
Apo B and apo A-I measurements are not routinely available, Vasan said, but are offered at some labs.
For years, researchers have debated whether measurement of the apolipoproteins should be added routinely to predict a person's heart disease risk.
But it seems that the old standby, "total cholesterol over HDL, is capturing most of the information that is in the apo B over A-I measurement," Vasan said.
"If you know your total and HDL cholesterol, our data do not support the need for additional measurements of apo B and A-I," he said.
Physicians divide total cholesterol by HDL cholesterol to get a ratio of total cholesterol to the healthy HDL cholesterol, Vasan explained. "A ratio below 3.5 is ideal," he said. For instance, if total cholesterol is 150 and HDL is 50, the ratio is 3, and the risk for heart disease is low.
If total cholesterol is 175 and HDL is 50, the ratio is 3.5.
Figuring the apo B to apo A-I ratio gives the balance of proteins that cause build up in the arteries with those that help prevent it.
One expert agreed with the researchers' conclusions, but with one caveat.
Dr. Scott Grundy, a professor of internal medicine and distinguished chair in human nutrition at the University of Texas Southwestern Medical Center at Dallas, said that predicting heart disease risk should also take into account other risk factors gleaned from the long-running Framingham Heart Study. These include factors such as age, gender, systolic blood pressure (the top number in the blood pressure reading), whether the person is on treatment for high blood pressure and whether the person smokes.
Total cholesterol below 200 milligrams per deciliter is desirable, according to the National Cholesterol Education Program. HDL levels of 60 mg/dl and higher are heart-protective, while HDL levels below 40 are considered low.
There's more on battling cholesterol at the U.S. National Heart, Lung and Blood Institute .