Title : A Better Cholesterol Test?
link : A Better Cholesterol Test?
A Better Cholesterol Test?
About twenty years ago, people started to realize that measuring total cholesterol wasn’t enough—you need to know your HDL and LDL breakdowns in order to best assess your risk. Along came the fasting full-lipid test. Now, some people are arguing that that isn’t enough either. They say that measuring your LDL and HDL subfractions, along with other lipoproteins, gives you the best idea of which treatments are right for you. (Subfractions are basically just further breakdowns of the category of LDL or HDL, similar to how you could break down the category of low-fat milk into skim, 1 percent, and 2 percent.) A few companies offer these tests—namely Atherotec, Berkeley Heart Labs, and Liposcience. Though each uses a different method to get to the result, all of them generally measure the same things:
Direct LDL Measurement
In the basic lipid profile, LDL cholesterol is calculated by using a mathematical formula based on the
measurements of triglyceride, total cholesterol, and HDL cholesterol levels. While this method has been widely used as the gold standard for determining LDL cholesterol levels for about forty years, it can be inaccurate under certain conditions. The higher the triglyceride level (especially above 250 mg/dL), the greater the potential error in calculation of the LDL value. According to some, this calculation can be off as much as 25 percent. And the worst part is that it underestimates the LDL level, making people think they have a healthier cholesterol level than they really do.
Newer tests measure the LDL cholesterol level directly, and they do not require that the blood sample come from a patient who has fasted for twelve hours. Although the accuracy and reproducibility of these tests have been more variable than I would like to see, they have been improved over the past few years and are widely used.
Measures for Different Types of LDL
Using these advanced tests, LDL gets broken down into two categories—one of which is smaller and denser than the other. Higher levels of the small, dense LDL are associated with higher rates of heart disease, partly because these smaller LDL can penetrate more easily into the lining of the arteries. A few large studies have found that high levels of small, dense LDL triple a person’s risk for heart disease. Small, dense LDL particles also can’t be reabsorbed by the liver as easily,
which gives them more time to do their damage.
Measures for Different Types of HDL
Similarly, HDL can be subclassified into denser and less dense particles. In this case, the different HDL particles are known as HDL 2 (less dense) and HDL 3 (more dense). Routine laboratory tests do not differentiate these two HDL particles—they just lump them together—but these more advanced tests do.
It is good to have high levels of both HDL 2 and HDL 3, but most studies indicate that high HDL 2 levels may be more potent in lowering your risk of heart disease than high HDL 3 levels. In a study of 1,799 Finnish men, for example, the risk of a heart attack was four times greater in men with low HDL 2 levels, three times greater in men with low HDL levels (not distinguishing HDL 2 from HDL 3), and only two times greater in men with low HDL 3 levels. Thus, it was low HDL 2 levels that carried the greatest risk. Stated another way, someone with particularly high HDL 2 levels would have the greatest protection.
Measures for Remnant Lipoproteins
Remnant lipoproteins (also called intermediate-density lipoproteins) are the particles that are trapped in between the conversion of triglyceride-rich VLDL to cholesterol-rich LDL. These particles are relatively rich in both triglyceride and cholesterol and can penetrate into the artery wall to stimulate atherosclerosis in much the same way that LDL particles do.
Measures for Lp(a)
Lp(a) is an emerging risk factor for heart disease, and these new tests can measure for Lp(a) at the same time as measuring your other lipoprotein levels.
That is A Better Cholesterol Test?
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