Question from a reader: "My doctor finally performed the advanced lipoprotein analysis I had been asking for. He said that I have something called LDL pattern B. He said that there's no drug treatment for it. In fact, I don't think he knew what to do. What does ‘LDL pattern B' mean and what can I do about it?"
First of all, "advanced lipoprotein analysis" is simply a blood test that is the next level beyond standard cholesterol testing. It gets away from the idea that cholesterol can be measured to estimate the amount of lipoproteins ("lipid-carrying proteins"), but directly measures the lipoproteins that cause heart disease.
"LDL pattern B" simply means that you have a substantial proportion of low-density lipoprotein (LDL) particles (often wrongly called "LDL cholesterol") that are abnormally small. If you have mostly large LDL particles, that's called "LDL pattern A."
All LDL particles are pretty small to begin with. They are several-fold larger than a cholesterol molecule, but hundreds of times smaller than a red blood cell. They are therefore measured in nanometers (nm), with one nanometer equaling one-millionth of a meter. Large LDL particles measure around 27 nm in diameter, while small LDL particles measure around 24 nm.
That modest size difference of about 3 nm accounts for widely divergent behavior. The configurations of the two complex particles differ, with the main protein of LDL particles, apoprotein B, assuming a unique shape when the particle is downsized. The contents of the two LDL particles also differ, with smaller LDL particles having greater triglyceride content and less cholesterol.
Differing shape and contents means that small LDL particles:
--Are not cleared from the bloodstream as rapidly as the more normal large LDL particles, since the LDL receptor recognizes them less effectively. Small LDL of pattern B therefore hang around much longer, providing more opportunity to cause atherosclerotic plaque.
--Are more adherent to the artery wall, making them more likely to trigger plaque formation.
--Are more potent triggers of inflammatory responses of the sort that make atherosclerotic plaque grow.
--Are more prone to oxidation, making them more powerful triggers of inflammation.
--Are more prone to glycation, or the glucose-triggered modification of the apoprotein B that makes it much more likely to contribute to atherosclerotic plaque.
The percentage of abnormally small LDL particles required to be labeled "LDL pattern B" differs. Some laboratories say 30% or more small LDL should be called "LDL pattern B," while others use a cutoff of 50% or more.
So what is labeled "LDL pattern B" differs from one laboratory to the next. A better way to look at small LDL is to only look at the percentage small LDL or the total quantity of small LDL and not worry about "pattern A" or "pattern B."
For example, in one lipoprotein technique called Vertical Auto-Profile, or VAP, offered by the Atherotech laboratory, if you have 60% small LDL particles and your total LDL is 150 mg/dl, then you have 90 mg/dl small LDL (60% of 150). You don't even have to worry about what the lab's cutoff is for small LDL.