This is a calculated ratio derived from the results of low-density lipoprotein (LDL-C) and high-density lipoprotein (HDL-C) tests in blood serum. This ratio reflects the balance between cholesterol that contributes to atherosclerosis (LDL) and cholesterol that protects against it (HDL), and it is considered an independent and more accurate predictor of coronary heart disease risk than measuring either cholesterol alone.