Apolipoprotein A1, Plasma
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Apolipoprotein A1 (ApoA1) is the primary protein associated with high-density lipoprotein (HDL) particles, and plays a central role in reverse cholesterol transport.(1) HDL cholesterol (HDL-C) and ApoA1 concentrations are inversely related to the risk for coronary artery disease (CAD).(2) There are a variable number of ApoA1 proteins per HDL particle. Therefore, ApoA1 is not a 1:1 surrogate marker for HDL particles. Similarly, the number of ApoA1 proteins and the amount of cholesterol contained in HDL particles is highly variable. This heterogeneity has led to unique clinical findings related to ApoA1 compared with HDL-C.
Increased ApoA1 concentrations are more strongly associated with a reduction in risk of a first myocardial infarction than HDL-C concentrations.(3) Low concentrations of ApoA1, but not HDL-C, are predictive of preclinical atherosclerosis as assed by computed tomography estimated coronary artery calcium (CAC) scoring.(4) Increased ApoA1, but not HDL-C concentrations, are associated with reduced cardiovascular events among statin-treated patients, even when LDL-C <50 mg/dL.(5) In statin-treated patients, patients whose ApoA1 increased while on treatment were at lower risk than those whose ApoA1 did not increase.
Evaluation of risk for atherosclerotic cardiovascular disease
Helpful to aid in the detection of Tangier disease
Low levels of apolipoprotein A1 (ApoA1) confer increased risk of atherosclerotic cardiovascular disease.
ApoA1 <25 mg/dL may be helpful to aid in the detection of a genetic disorder such as Tangier disease.
Expected values in normal (no cardiovascular or genetic disease) adults are 106 to 220 mg/dL ApoA1.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Fasting for <12 hours or intake of alcohol during the 24 hours prior to specimen collection may invalidate test results.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
> or =18 years: 106-220 mg/dL
Reference values have not been established for patients that are <18 years of age.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Sorci-Thomas MG, Thomas MJ: Why Targeting HDL Should Work as a Therapeutic Tool, but Has Not. J Cardiovasc. Pharmacol 2013;62:239-246
2. Di Angelantonio E, Sarwar N, Perry P, et al: Emerging Risk Factors Collaboration. Major lipids, apolipoproteins, and risk of vascular disease. JAMA 2009;302:1993-2000
3. McQueen MJ, Hawken S, Wang X, et al: Lipids, lipoproteins, and apolipoproteins as risk markers of myocardial infarction in 52 countries (the INTERHEART study): a case control study. Lancet 2008;372:224-233
4. Sung KC, Wild SH, Byrne CD: Controlling for apolipoprotein A-I concentrations changes the inverse direction of the relationship between high HDL-C concentration and a measure of pre-clinical atherosclerosis. Atherosclerosis 2013;231:181-186
5. Boekholdt SM, Arsenault BJ, Hovingh GK, et.al: Levels and Changes of HDL Cholesterol and Apolipoprotein A-I in Relation to Risk of Cardiovascular Events Among Statin-Treated Patients: A Meta-Analysis. Circulation 2013;128:1504-1512