Apolipoprotein A1 (ApoA1) is important for assessing the risk of atherosclerotic cardiovascular disease and diagnosing Tangier disease. It plays a key role in reverse cholesterol transport, with higher ApoA1 levels more strongly associated with reduced risk of a first myocardial infarction than HDL-C concentrations. Additionally, low ApoA1 levels can predict preclinical atherosclerosis based on coronary artery calcium scoring.