Researchers have developed a more accurate way to calculate "bad" cholesterol that can lead to hardening of the arteries and increase the risk of heart attack and stroke.
Current methods to measure low-density lipoprotein (LDL) cholesterol are believed to underestimate heart disease danger among many high-risk patients. But a new method, developed by John Hopkins researchers, could provide a much more accurate assessment.
"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," says Seth S. Martin, M.D., lead study author.
Many studies have shown that higher levels of LDL cholesterol signal greater risk of plaque accumulating in heart arteries. Since 1972, a formula called the Friedewald equation has been used to gauge LDL cholesterol. It is an estimate rather than a direct measurement. However, physicians use the number to assess their patients' risk and determine the best course of treatment.
The problem, says researchers, is that the measurement applies a one-size-fits-all technique. The newly developed system uses 180 different factors to assess patients individually, with more accuracy.
Using a database of blood lipid samples from more than 1.3 million Americans that were directly measured with a traditional and widely accepted technique known as ultracentrifugation, the researchers developed an entirely different system and created a chart that uses 180 different factors to more accurately calculate LDL cholesterol and individualize the assessment for patients.
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"We believe that this new system would provide a more accurate basis for decisions about treatment to prevent heart attack and stroke," says Martin. They found that in nearly one out of four samples in the "desirable" range for people with a higher heart disease risk, the Friedewald equation was not accurate.
The study is published in the Journal of the American Medical Association.