High levels of “bad” cholesterol increase the risk of both heart attack and stroke, but the current one-size-fits-all formula for determining this important value underestimates the risk for many people.
Researchers at Johns Hopkins University, though, have developed a new method that could give patients and their doctors a more accurate assessment of their level of “bad”—or low-density lipoprotein (LDL)—cholesterol.
"The standard formula that has been used for decades to calculate LDL cholesterol often underestimates LDL where accuracy matters most—in the range considered desirable for patients at high risk for heart attack and stroke," Dr. Seth S. Martin, first author on the new study released that will come out Tuesday in the Journal of the American Medical Association, said in a press release.
'Bad' Cholesterol Linked to Risk of Heart Disease
When high levels of LDL cholesterol circulate in the blood, it can build up on the inner walls of the arteries to form a hard deposit called a plaque. This condition, known as atherosclerosis, increases the risk of heart attack and stroke.
Doctors frequently use LDL level—along with other factors such as high blood pressure and smoking—to determine a patient’s risk of heart disease and to determine the best course of treatment.
While LDL cholesterol can be measured directly using specialized laboratory equipment called an ultracentrifuge, it is not part of a standard lipid profile, which also includes total cholesterol, HDL ("good") cholesterol, and triglycerides. To avoid the added expense of an extra test, LDL cholesterol is commonly estimated using an equation developed decades ago. This formula is based upon the blood levels of total cholesterol, HDL cholesterol, and triglycerides.
The equation also includes an adjustment factor for triglycerides, which is applied equally to every person. Doing this, however, underestimates the risk of heart disease for some.
“Many people—especially those with high triglyceride levels—may have a false sense of assurance that their LDL cholesterol is at an ideal level,” Dr. Steven Jones, M.D., senior author on the new study, said. “Instead, they may need more aggressive treatment to reduce their heart disease risk.”
New Adjustable Method of Estimating LDL Levels
To improve the LDL level estimates for all people, the researchers turned to a database of blood samples from 1.3 million Americans. The LDL and other blood lipid values in the database were measured directly—and accurately—by a laboratory in Alabama using ultracentrifugation.
Developing the new method for estimating LDL, however, was the result of more than just a large database.
"It was made possible by the sheer size of the lipid sample, modern computing power, and the intellectual framework for our analysis," Martin told Healthline.
The resulting chart takes into account a person’s cholesterol and triglyceride levels and is based upon 180 different factors. It provides a more accurate assessment of the LDL cholesterol as well as the risk of heart disease.
The accuracy of the new method still needs to be confirmed through further studies, but if adopted by the medical laboratories that routinely test blood samples, it could help doctors better assess a person’s risk.
Although a new guideline for cholesterol treatment may change how doctors prescribe cholesterol-lowering drugs by identifying high-risk groups that would benefit from statins, LDL cholesterol will continue to play a role.
"Our new method for estimating LDL cholesterol remains extremely important for physicians around the world," Martin said.