Which value would be considered the greatest risk factor associated with coronary artery disease?

The greatest risk factor associated with coronary artery disease in this context is represented by the level of high-density lipoproteins (HDL). HDL is often referred to as "good" cholesterol because it helps transport cholesterol away from the arteries and toward the liver, where it can be processed and eliminated from the body. A low level of HDL cholesterol, such as 20 mg/dL, indicates inadequate protective mechanisms against cardiovascular events, increasing the risk for coronary artery disease.

In evaluating the other values provided, while low-density lipoproteins (LDL), diastolic blood pressure, and systolic blood pressure are all relevant to cardiovascular health, they do not carry the same level of risk associated with coronary artery disease as the low HDL levels do. Elevated LDL cholesterol levels contribute to plaque buildup in arteries, and high blood pressure (whether systolic or diastolic) is a well-known risk factor for cardiovascular issues, but low levels of HDL significantly detract from cardiovascular protection and are a direct indication of increased risk for disease. Thus, the level of 20 mg/dL HDL serves as a considerable risk factor that underscores the importance of maintaining higher HDL levels to mitigate the risk of coronary artery disease.