ApoB and Cardiovascular Risk

In Cholesterol Tests Your Doctor Hasn’t Told You About, I briefly describe a cholesterol blood test for Apolipoprotein B (ApoB).  This simple blood test measures the number and size of LDL (bad) cholesterol: it’s an important test if you have high LDL (bad) cholesterol or are at ‘high risk’ of cardiac disease, as it provides a more finely tuned assessment of cardiovascular risk.

In fact, it might be a critical test for those with low LDL (bad) cholesterol – because it can reveal hidden cardiac risk.

While studies show ApoB is a better predictor of cardiac risk, it is not yet a test that is widely prescribed. Indeed, the American Heart Association is waiting for more studies to determine if ApoB is a test doctors should recommend. Personally, I find this frustrating (of course this means nothing as I’m not a doctor, but…) To me, it’s frustrating because this is a simple blood test that provides a detailed risk assessment.

Scientific American’s Heart Health Special Report entitled ApoB – A Better Marker For Heart Attack Risk Than LDL-Cholesterol explains why it’s an effective and important test:

“A high level of low-density lipoprotein (LDL, or “bad”) cholesterol is an important risk factor for a heart attack. Yet about half of the people who develop coronary heart disease have normal or even low LDL cholesterol levels. Some research suggests that a component of LDL—called apolipoprotein B, or apo B—may be more accurate at predicting coronary heart disease.

A Limitation with LDL Cholesterol Testing
The problem with using LDL cholesterol levels to determine heart attack risk is that the test measures only the amount of cholesterol in the LDL cholesterol particles, not the number or size of these particles. Apo B measurements, on the other hand, provide information on the number of LDL cholesterol particles.

For example, people with a higher apo B value than LDL cholesterol value tend to have smaller, denser LDL cholesterol particles. Studies have shown that small, dense LDL cholesterol particles are more strongly associated with heart attack risk than large, “fluffy” LDL cholesterol particles.

The test itself is a simple blood test. It’s easy and cheap: easier, even than the standard cholesterol lipid panel as it does not require fasting.  In fact, the test can be done in conjunction with a standard lipid panel.

Finally, after I visited a cardiologist, I got the ApoB test and my results were, of course, mixed.

Ha! ha ha ha ha ha ha ha

Part of the problem is that since ApoB testing isn’t a standard test there is conflicting info on what the goal ApoB levels should be. My cardiologist was happy with my results because my ApoB is lower than my LDL level, my LDL Pattern is the far healthier Type A / Fluffy LDL, and because my C-Reactive Protein was low risk (more on C-Reactive Protein and LDL patterns in another post.).

But my actual lab report shows my ApoB level of 123 as ‘high risk’ and simply references a desired range of 49-103.  So at 123, I have ‘high’ ApoB.

Ruh Roh.

Who to believe?

Well, it’s simple.  My cardiologist. After a lot of online research (again, I’m no doctor so take all this with a grain of salt), I think the reason my cardiologist is OK with my ApoB score of 123 is because of all those elements I mention above AND ALSO because  I fall into the ‘low risk’ of cardiac disease segment. It turns out that there are different ApoB goals based on a person’s general cardiac disease risk, and the lab report seems not to take this into account.

ApoB goals by risk pool is well explained in Medscape’s emedicine article entitled Apoliprotein B article, in the chart here:

Screen Shot 2015-03-14 at 5.22.44 PM

 

Since my 10 year risk factor via the cardiac disease risk calculator is low (and I also have just 1 risk factor from the ‘old’ way of calculating risk), then it’s probably OK that my ApoB is 123 as it’s lower than 130.

I’m glad I got the ApoB test done – but it’s only because I asked two doctors for it.  If you want a more detailed risk assessment, ask your internist or cardiologist about ApoB testing.

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Cholesterol Tests Your Doctor Hasn’t Told You About

A standard cholesterol lipid panel  provides four measures: Total Cholesterol, LDL Cholesterol, HDL Cholesterol and Triglycerides.  But did you know that there are two other blood tests — and one ratio that’s easy to calculate — that can better predict your risk of heart disease?  Which means that even with high cholesterol, you might not need a statin medication if these tests show low cardiac disease risk.

Or you might think you don’t need a statin … and in fact do.

And yet, your doctor probably has not told you about these tests.  So let me.

Apolipoprotein B – or as it’s commonly referred to, ApoB, is a simple blood test that measures the number and size of LDL (bad) cholesterol. Why this test is useful is well explained by Johns Hopkins Health Alerts:

“The problem with using LDL cholesterol levels to determine heart attack risk is that the test measures only the amount of cholesterol in the LDL cholesterol particles, not the number or size of these particles. Apo B measurements, on the other hand, provide information on the number of LDL cholesterol particles.

For example, people with a higher apo B value than LDL cholesterol value tend to have smaller, denser LDL cholesterol particles. Studies have shown that small, dense LDL cholesterol particles are more strongly associated with heart attack risk than large, “fluffy” LDL cholesterol particles.”

So if you have high LDL cholesterol (goal is under 130), you might want to find out if you have the ‘fluffy’ kind of LDL (pattern A), or the more dangerous, small, dense type of LDL (pattern B). Indeed, the Johns Hopkins Health Alert goes on to explain, “Research published in The Lancet reviewed five studies of LDL cholesterol and ApoB in nearly 200,000 people. The researchers concluded that high levels of ApoB were more strongly linked with future heart attack risk than LDL cholesterol levels.”  Compelling, no?

Low Density Particle Number, or LDL-P, is a similar measure – and again, one that’s been shown to be a more accurate predictor of heart disease than the typical cholesterol measurements.  LDL-P measures the number of LDL particles in the blood, whereas LDL is just the total LDL cholesterol.

As explained in The Difference Between LDL-C and LDL-P on the Primal Docs website, two people with the same LDL numbers can have vastly different heart disease risk because one has low LDL-P (fewer LDL particles of the type A, big, fluffy kind) while the other has high LDL-P, or a lot of LDL particles, of the small, dense, type B kind:

“…one person (person A) may have large cholesterol rich LDL particles, while another (person B) may have smaller cholesterol depleted particles. These two persons may have the same LDL-C concentration. However, person B will have higher LDL particle number (LDL-P). Despite similar levels of LDL-C, person B is at higher risk four future cardiovascular events. Furthermore, person B will have more small LDL-particles.”

The doctor who wrote this explanation of LDL-C vs. LDL-P goes on to explain that both LDL-P and ApoB are stronger predictors of heart disease risk than typical cholesterol measures:

“Some studies have suggested that the size of LDL-particles may be of importance. People whose LDL particles are predominantly small and dense, have a threefold greater risk of coronary heart disease.

ApoB and LDL-P both reflect the number of atherogenic lipoprotein particles. Measurements of ApoB and LDL-P are better predictors of cardiovascular disease risk than LDL-C. Furthermore, ApoB and LDL-P may predict residual risk among individuals who have had their LDL-C levels lowered by statin therapy.”

Non-HDL Cholesterol is a third important measure — and you don’t even need to take a blood test. Non-HDL-C is simply your Total Cholesterol minus HDL Cholesterol.  The tricky part is figuring out goal: if your LDL cholesterol is “at goal” you can roughly estimate your non-HDL-C goal by simply adding 30 to your LDL goal (these goals are usually on the cholesterol report – they are also online or you can ask your doctor.) And if it’s not at goal, discuss this ratio with your doctor.  I wrote about non-HDL-C and how to calculate it in this blog post, Do You Know Your Non-HDL Cholesterol?

While researching these in-depth cholesterol tests, I came across this compelling medical case study. It socked me in the gut, as this woman’s lipid panel cholesterol results were similar to mine, and yet it turns out from the additional LDL-P and ApoB testing that she was at high risk for cardiac disease. And needed statins.

Gulp.

So how do you get these tests?

I asked my internist about them months ago, and she said I didn’t need them — that my cholesterol numbers are fine. But now that I’ve read this case study I feel I would love more information.  I’ll have to ask her again about additional testing – especially now that I have more info.

And just so you know, you don’t have to travel to the Cleveland Clinic or the Mayo Clinic or Berkeley, California to get these tests. The Johns Hopkins Health Report explains,

“One widely used test, called the NMR LipoProfile, analyzes the size of lipoprotein particles in the blood by measuring their magnetic properties. Several others, including the LipoPrint and the Berkeley (from Berkeley HeartLab) use electrical fields to distinguish the size and other attributes of lipoprotein particles. Still another, known as the VAP (for Vertical Auto Profile) test, separates lipoprotein particles using a highspeed centrifuge.”

Even though my cholesterol is at goal, I’ve got to put in a call to my internist to ask about getting both the LDL-P and ApoB testing done. Will keep you posted.

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