Apolipoprotein Evaluation (Apo-A-1, Apo-B, Lp(a))
The Apolipoprotein Evaluation measures Apo-A-1, Apo-B, and Lp(a) to quantify HDL and atherogenic lipoprotein particle number and identify genetic Lp(a) elevation. Apo-B counts all atherogenic particles, Apo-A-1 reflects HDL particle number, and Lp(a) is a heritable risk factor unresponsive to most therapy, refining cardiovascular risk stratification beyond cholesterol concentrations.
4
Biomarkers
Blood (serum)
Sample
3–5 business days
Turnaround
Preferred (12 hours)
Fasting
What is the Apo Panel test?
The Apolipoprotein Evaluation measures Apo-A-1, Apo-B, and Lp(a) to quantify HDL and atherogenic particle number directly and to identify genetically elevated Lp(a), providing a more granular assessment of cardiovascular risk than cholesterol concentrations alone. Traditional lipid panels measure cholesterol mass carried by lipoproteins, but particle number often diverges from cholesterol content—particularly when triglycerides are high, HDL is dysfunctional, or LDL particles are small and dense. Because each atherogenic particle contains one Apo-B molecule and each HDL particle carries multiple Apo-A-1 molecules, apolipoprotein concentrations directly quantify particle burden. Lp(a) adds a heritable, largely treatment-resistant dimension: it is measured once to unmask individuals whose elevated risk will not be captured or modified by conventional lipid-lowering therapy. Together, Apo-A-1, Apo-B, and Lp(a) refine risk stratification, guide intensity of therapy, and identify residual risk when standard lipid targets have been met.
What does the Apo Panel test measure?
Apolipoprotein A-1 is the principal structural and functional protein of high-density lipoprotein particles. It activates lecithin-cholesterol acyltransferase, which esterifies free cholesterol on the HDL surface, and serves as the ligand for hepatic HDL receptors that mediate reverse cholesterol transport. Each HDL particle carries multiple Apo-A-1 molecules, making Apo-A-1 concentration a direct measure of HDL particle number rather than cholesterol content.
Low Apo-A-1 reflects reduced HDL particle number and impaired reverse cholesterol transport, conferring elevated cardiovascular risk even when HDL-cholesterol appears adequate. Apo-A-1 is a stronger inverse predictor of coronary events than HDL-C in many cohorts and is particularly useful when HDL particle size or composition is altered by diabetes, hypertriglyceridaemia, or inflammatory states.
Apolipoprotein B is the obligate structural protein of atherogenic lipoproteins: each VLDL, IDL, LDL, and lipoprotein(a) particle contains exactly one Apo-B molecule. Because LDL particles dominate the circulating Apo-B pool in the fasting state, Apo-B concentration directly quantifies the total number of atherogenic particles, independent of their cholesterol or triglyceride cargo.
Apo-B is a superior marker of atherogenic particle burden and cardiovascular risk than LDL-cholesterol, particularly when triglycerides are elevated or LDL particles are small and dense. It identifies residual risk in patients whose LDL-C is at target but whose particle number remains high, and guidelines increasingly recognise Apo-B <80 mg/dL as a treatment goal for high-risk patients.
Lipoprotein(a) is an LDL-like particle covalently linked to apolipoprotein(a), a large, highly polymorphic glycoprotein with sequence homology to plasminogen. Lp(a) concentration is predominantly determined by the LPA gene and remains stable throughout adult life, varying more than 1,000-fold between individuals. It promotes atherogenesis through cholesterol delivery and may also impair fibrinolysis and promote inflammation.
Elevated Lp(a) is an independent, causal risk factor for atherosclerotic cardiovascular disease and calcific aortic stenosis. Because it is genetically determined and unresponsive to most lipid-lowering therapies, measurement is recommended once to identify individuals who require more aggressive management of modifiable risk factors. Values >50 mg/dL (or >125 nmol/L) confer significantly elevated risk.
The Apo-B/Apo-A-1 ratio integrates the atherogenic particle burden (Apo-B) with the cardioprotective HDL particle count (Apo-A-1), reflecting the balance between cholesterol delivery to and removal from the arterial wall.
The Apo-B/Apo-A-1 ratio predicts cardiovascular events more robustly than traditional lipid ratios in multiple cohorts and is particularly useful when triglycerides are elevated or HDL particle function is impaired. A high ratio indicates that atherogenic particles outnumber protective ones, signalling elevated residual risk even when LDL-C and HDL-C appear acceptable.
Why is the Apo Panel test ordered?
- Patients with a family history of premature cardiovascular disease or elevated Lp(a), for whom a single Lp(a) measurement informs lifelong risk stratification
- Individuals with metabolic syndrome, type 2 diabetes, or hypertriglyceridaemia, where discordance between LDL-C and Apo-B is common and particle number predicts risk more accurately
- Patients whose calculated cardiovascular risk is intermediate and in whom apolipoprotein measurement may reclassify risk to guide statin or other preventive therapy
- Monitoring of lipid-lowering therapy when LDL-C and non-HDL-C targets have been achieved but residual risk is suspected, particularly if Apo-B remains elevated
- Evaluation of patients with low HDL-cholesterol or high triglycerides, where Apo-A-1 and the Apo-B/Apo-A-1 ratio capture HDL particle number and the atherogenic-protective balance more precisely
- Cascade screening of first-degree relatives when a proband has very high Lp(a), as Lp(a) is inherited in an autosomal codominant fashion
- Assessment of young adults (<40 years) with atherosclerotic disease or stroke of uncertain aetiology, where unrecognised elevated Lp(a) may be causal
- Recurrent cardiovascular events despite optimal lipid management, prompting investigation of non-modifiable genetic risk factors such as Lp(a)
Sample collection and turnaround
Sample type
Blood (serum)
Fasting required
Preferred (12 hours)
Collection method
Venipuncture at patient service centre
Turnaround
3–5 business days
Collection notes
Phlebotomy at the patient service centre; fasting for 12 hours is preferred to minimise triglyceride interference with Apo-B, though Apo-A-1 and Lp(a) are minimally affected by fasting status. Measure in a stable metabolic state, not during acute illness, hospitalisation, or within 4–6 weeks of myocardial infarction, surgery, or other major physiological stress.
Specimen requirements
Minimum 1 mL serum. Separate from cells promptly and store refrigerated or frozen if processing is delayed. Note the performing laboratory for serial comparability, particularly for Lp(a), because assays and reference intervals differ.
What can affect Apo Panel results?
Apo-A-1 may fall during acute illness or injury because HDL serves as a negative acute-phase reactant; Apo-B may also be transiently altered. Measure apolipoproteins in a stable metabolic state, not during acute hospitalisation or within weeks of myocardial infarction or surgery.
Postprandial triglyceride-rich lipoproteins carry Apo-B, so non-fasting samples may overestimate Apo-B modestly. Fasting is preferred for Apo-B and improves comparability; Apo-A-1 and Lp(a) are minimally affected by fasting status.
Oestrogen raises Apo-A-1 and lowers Apo-B, while pregnancy increases triglycerides and alters lipoprotein composition. Interpretation should account for hormonal state; Lp(a) is less affected but may rise modestly in pregnancy.
Lp(a) assays are not fully standardised and results reported in mass units (mg/dL) are confounded by apolipoprotein(a) size polymorphism, whereas molar units (nmol/L) are preferred but not universally available. Serial measurements should use the same laboratory and method.
Chronic kidney disease raises Lp(a) independently of LPA genotype, likely through reduced catabolism. Elevated Lp(a) in CKD still confers cardiovascular risk, but the elevation is partly acquired rather than purely genetic.
Statins lower LDL-C more than Apo-B, revealing particle-cholesterol discordance. Niacin lowers Lp(a) modestly; PCSK9 inhibitors lower both Apo-B and Lp(a). Because Lp(a) is largely treatment-resistant, it is measured before or early in therapy to guide baseline risk assessment.
What do Apo Panel results mean?
Elevated
Elevated Apo-B (>100 mg/dL, or >80 mg/dL in high-risk patients) reflects an increased number of atherogenic particles and predicts cardiovascular events independently of LDL-C. Elevated Lp(a) (>30 mg/dL or >75 nmol/L, with very high risk at >50 mg/dL or >125 nmol/L) is a genetic, causal risk factor for atherosclerosis and aortic stenosis and signals the need for aggressive management of modifiable risk factors. A high Apo-B/Apo-A-1 ratio (>0.9) indicates that atherogenic particles outnumber protective HDL particles, conferring elevated risk even when cholesterol levels appear acceptable.
Normal
Apo-A-1, Apo-B, and Lp(a) within reference ranges indicate average particle burden and genetic Lp(a) risk, but cardiovascular risk stratification requires integration with the full lipid panel, clinical risk factors, and, where available, coronary artery calcium scoring. Normal Apo-B does not exclude risk if other atherogenic factors are present, and a single normal Lp(a) measurement suffices because Lp(a) is stable throughout adult life.
Reduced
Low Apo-A-1 (<120 mg/dL in men, <140 mg/dL in women) reflects reduced HDL particle number and impaired reverse cholesterol transport, raising cardiovascular risk. Low Apo-B (<40 mg/dL) is uncommon outside severe malnutrition or genetic lipoprotein deficiency and is not typically a therapeutic concern. Very low Lp(a) (<10 mg/dL or <25 nmol/L) is favourable and confers lower cardiovascular risk, though no intervention lowers Lp(a) to these levels reliably.
Note: Apo-B is the preferred marker when triglycerides are elevated or when discordance exists between LDL-C and calculated non-HDL-C or particle number. Lp(a) should be measured once for risk stratification; it does not respond meaningfully to diet or most lipid therapies, so serial monitoring is not useful unless specific Lp(a)-lowering therapy (investigational or newly approved agents) is initiated. Assay standardisation for Lp(a) remains incomplete—compare results only within the same laboratory and method, and confirm whether the laboratory reports mass or molar units. The Apo-B/Apo-A-1 ratio integrates both markers and may outperform either alone in risk prediction, but it is not yet embedded in all guidelines.
Frequently asked questions
Apo-B quantifies the total number of atherogenic particles (VLDL, IDL, LDL, Lp(a)), because each particle contains exactly one Apo-B molecule. LDL-cholesterol measures the cholesterol mass carried by LDL particles. When triglycerides are elevated or particles are small and dense, LDL-C underestimates particle number and Apo-B is the more accurate predictor of cardiovascular risk.
How to access the Apo Panel test
The Apo Panel reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.
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Published: October 7, 2026
Last reviewed: October 7, 2026
- Mach F, et al. 2019 ESC/EAS guidelines for the management of dyslipidaemias: lipid modification to reduce cardiovascular risk. Eur Heart J. (2020)
- Grundy SM, et al. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA guideline on the management of blood cholesterol. Circulation. (2019)
- Nordestgaard BG, et al. Lipoprotein(a) as a cardiovascular risk factor: current status. Eur Heart J. (2010)
- Sniderman AD, et al. Apolipoprotein B particles and cardiovascular disease: a narrative review. JAMA Cardiol. (2019)
- Tsimikas S, et al. NHLBI working group recommendations to reduce lipoprotein(a)-mediated risk of cardiovascular disease and aortic stenosis. J Am Coll Cardiol. (2023)
- Walldius G, et al. The apoB/apoA-I ratio: a strong, new risk factor for cardiovascular disease and a target for lipid-lowering therapy. J Intern Med. (2006)
This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.