The Quebec Cardiovascular Study was the first large study demonstrating that heart attack can occur when a person’s LDL particle number is high and LDL level is low. 8 This has been repeatedly confirmed in other studies, most recently in the AMORIS study, which enrolled a remarkable 175,000 participants and demonstrated the superiority of LDL particle number (measured as apoprotein B) in predicting heart attack risk. 9 This measure can be thought of as actually counting the number of LDL particles in one cubic centimeter, or one milliliter of blood.
LDL particle number is among the most powerful tools we have to predict the risk of heart attack. It can be measured directly as LDL particle number by the nuclear magnetic resonance spectroscopy method or indirectly as apoprotein B, which is a more widely available method. Apoprotein B is the major protein particle of LDL, with a single protein per LDL particle. Apoprotein B thus provides a “count” of LDL particles.