LDL pattern A suggests larger, more buoyant, less atherogenic LDL particles, while pattern B reflects smaller, denser LDL particles which are prone to oxidation and are more atherogenic.
The two main LDL patterns identified in lipoprotein subfractionation testing refer to LDL particle size. Pattern A reflects larger LDL particles 20.6-23 nm, which tend to be buoyant and less atherogenic. Pattern B reflects smaller, denser LDL particles 19-20.5 nm, which are more likely to be oxidized and cause atherosclerosis. Pattern B may be more likely to be associated with high serum triglycerides as well (Koba 2002, Mikhailidis 2011).
Nuclear magnetic resonance (NMR) testing measures LDL in nanometers (nm) (Labcorp NMR Lipoprofile®), while ion mobility measures LDL in Angstrom units (0.1 nm) (Quest Cardio IQ®). No matter which test is used, the smaller, denser LDL particles (sdLDL) and the cholesterol carried on them (sdLDL-C) are considered more atherogenic and more closely associated with coronary artery disease. Higher levels of sdLDL-C are also associated with metabolic syndrome and type 2 diabetes (Hirayama 2012).
You can read more about lipoprotein subfractionation testing on the ODX Research blog: https://www.optimaldx.com/research-blog/nmr-lipoprotein-subfractionation-beyond-cholesterol
References
Hirayama, Satoshi, and Takashi Miida. “Small dense LDL: An emerging risk factor for cardiovascular disease.” Clinica chimica acta; international journal of clinical chemistry vol. 414 (2012): 215-24. doi:10.1016/j.cca.2012.09.010
Koba, Shinji et al. “Small dense LDL phenotype is associated with postprandial increases of large VLDL and remnant-like particles in patients with acute myocardial infarction.” Atherosclerosis vol. 170,1 (2003): 131-40. doi:10.1016/s0021-9150(03)00245-4
Labcorp NMR Lipoprofile Sample Report. https://files.labcorp.com/testmenu-d8/sample_reports/123638.pdf
Mikhailidis, Dimitri P., et al. "" European panel on low density lipoprotein (LDL) subclasses": a statement on the pathophysiology, atherogenicity and clinical significance of LDL subclasses: executive summary." Current vascular pharmacology 9.5 (2011): 531-532.
Quest Cardio IQ® Ion Mobility test. https://www.questdiagnostics.com/healthcare-professionals/clinical-education-center/faq/faq134