If you’ve been following my blog for a while, you know that I’m a PhD chemist who’s a retired hospital administrator. One of the reasons I wanted a career in science/healthcare is that they are fields that require lifetime learning because of the fast pace at which information changes. I try to keep up to date with new advances in medicine, especially in several areas, such as new clinical laboratory tests that may help diagnose or monitor disease.
When I was at the medical center I used to give presentations to community groups and spoke about topics such as cholesterol and cardiovascular disease (think heart attacks). For many years the presentation didn’t change much:
Your blood cholesterol is one of several risk factors for heart attacks. You can change some risk factors, like smoking, hypertension (high blood pressure), your blood cholesterol level, etc. but some you can’t change, like age, sex, etc.
We’ve known for many decades that as your blood cholesterol level increases over 200 mg/dL, you tend to have a greater chance of having a heart attack. However, there are several different kinds of cholesterol in your blood. 20 years ago we knew that some kinds of cholesterol are bad (like LDL, Low Density Lipoprotein) and some are good (like HDL, High Density Lipoprotein). Although total cholesterol is important, it doesn’t tell the whole story: you can reduce your risk of a heart attack by lowering your LDL cholesterol (the bad kind) either with diet or with medications.
I used to end my presentations by saying, “Get your number down, before your number’s up!”.
Lowering LDL cholesterol to prevent heart attacks seems like a simple concept, except for one disturbing fact: half the people who have heart attacks have normal levels of total cholesterol and LDL cholesterol. We used to get around that problem by saying that cholesterol was only a small part of the overall picture, and that age, sex, blood pressure, smoking, etc. also had to be considered. That’s a greatly simplified version of what we thought back then.
For many years we determined the amount of LDL cholesterol by performing a routine “lipid panel”: measuring total cholesterol, HDL cholesterol and triglycerides (another kind of lipid) and then using an equation to calculate the LDL level. Eventually scientists discovered a way to actually test and measure LDL cholesterol itself, and found that there are several different kinds of LDL cholesterol. When we calculated or measured “LDL”, we had been talking about total LDL. It turns out that, just as there are several kinds of cholesterol, there are several different kinds of LDL. About 5 years ago, researchers began studying the various kinds of LDL cholesterol, and we began to refer to total LDL as LDL-C (think LDL concentration). Through advanced techniques like nuclear magnetic resonance (NMR) we can actually measure and count LDL particles, which we call LDL-P, and we can differentiate small LDL particles from big LDL particles. I know we’re covering a lot of information in a short time, but stay with me.
For many people the numbers for LDL-C and LDL-P tend to change at an equal rate. In other words, as the total LDL cholesterol goes up, the number of LDL particles goes up just as quickly. However, in some people, LDL-C goes up faster than LDL-P, and in other people LDL-C goes up slower than LDL-P. We call this “discordance”. This can be important, since a given person can have a normal amount of total LDL, but an elevated number of LDL particles.
Some very elegant clinical studies showed that LDL-P (the number of LDL particles) is a better indicator of future heart attack risk than just LDL-C (the total LDL concentration). In addition, small LDL particles tend to be more dangerous than large LDL particles. Is this the answer to the riddle of why half of heart attacks occur in patients with normal cholesterol and normal LDL-C? That may be an over simplification, but this newer information is so important that I recommend everyone have their LDL-P measured and compared to their LDL-C at least once as a baseline.
If you’ve never had your LDL-P measured, ask your physician to order it instead of just ordering the normal “lipid panel”. This is especially important if you or a family member has a history of heart disease. The specialized laboratory that performs this test is LipoScience in Raleigh NC, and the test itself is called “NMR LipoProfile”. In addition to giving you a number for LDL-P, the LipoProfile produces a battery of other test results, but we’ve already covered a lot of things, so let’s just stop here for now. Note: if your regular physician isn’t a cardiologist, he/she may not be familiar with LDL-P or the NMR LipoProfile.
If your LDL-P is low, great! You can save the results as a baseline and have it measured again in several years. However, if it’s elevated, your physician may want to monitor your response to diet and/or medications by using it to assess progress, rather than the usual way of using LDL-C.
I am neither affiliated with nor have a financial interest in LipoScience; I’m passing along the name for informational purposes only. If you’ve found this article interesting, you can get more information by searching online for “LDL-P”, “LipoProfile”, etc.
(732) 239-0739 (cell) (732) 530-6686 (office)