I saw a patient in the office yesterday. He came to me for an opinion regarding his high heart scan score of 525, putting him in the 90th percentile (5% annual risk of heart attack).
His doctor had been puzzled because his LDL cholesterols had ranged from 110 to 131 mg--actually below average. (The average LDL for the U.S. is 132 mg.) Likewise, HDL was a favorable 63 mg.
Lipoprotein analysis told the story loud and clear. His LDL particle number , a far more precise measure of LDL, was 2448 nmol/l. This means that his true LDL was more like 240-250 mg! (You can get a sense for what the true LDL is from LDL particle number by dropping the last digit: 2448 becomes 244.) Conventional LDL was therefore inaccurate by over 100 mg.
He also had a severe small LDL particle pattern. The cause of his coronary plaque was a large excess of small LDL particles. LDL cholesterol (and total cholesterol, likewise) didn't even hint at this pattern. Nor did his favorable HDL.
Think of LDL particle number as an actual count of LDL particles per volume, e.g., number of particles per cc of blood. This makes it easier to conceptualize. LDL particle number is the measure you get when you have an NMR lipoprotein profile, our preferred method of lipoprotein testing. If this is unavailable to you, apoprotein B is a reasonable second choice, though not as accurate in my view. More info on NMR is available at their website, www.lipoprofile.com.