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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