Beyond Standard Cholesterol: Why ApoB, Lp(a) and Lp-PLA2 Matter

A standard cholesterol test tells you how much cholesterol is being carried around in your blood. What it does not tell you is how many particles are carrying it, how prone those particles are to entering the artery wall, or whether inflammation is actively destabilising any plaque that has already formed.

For most people in most clinical contexts, the standard test is a reasonable starting point. For those who want a more complete picture of their cardiovascular risk, or who have had a cardiac event despite apparently normal cholesterol levels, it is not enough on its own. Three markers in particular, apolipoprotein B, lipoprotein(a) and lipoprotein-associated phospholipase A2, provide clinically significant information about cardiovascular risk that a standard lipid panel does not capture.

Understanding what each of them measures, and why it matters, is the starting point for anyone considering an advanced cardiovascular assessment.

What’s The Challenge With Measuring LDL Cholesterol Alone?

The standard lipid panel measures the amount of cholesterol carried within low-density lipoprotein particles, a figure referred to as LDL cholesterol or LDL-C. It has been the dominant marker of cardiovascular risk for decades, and its association with atherosclerosis is well established.

However, the cholesterol content of individual LDL particles is not fixed. It varies considerably between people, meaning that two individuals with an identical LDL cholesterol reading may have very different numbers of LDL particles in circulation, and therefore very different levels of actual atherogenic risk.¹

Because each particle has the potential to penetrate the artery wall and contribute to plaque formation, particle number, not cholesterol mass, is what determines exposure risk. A person with many small, cholesterol-depleted particles may show a reassuringly normal LDL cholesterol result while carrying a substantially elevated number of atherogenic particles in their circulation.² This is the gap that apolipoprotein B is designed to close.

What Does Apolipoprotein B Measure?

Apolipoprotein B is the protein that sits on the surface of every atherogenic lipoprotein particle, including LDL, intermediate-density lipoprotein, very low-density lipoprotein and lipoprotein(a). Because each of these particles carries exactly one apolipoprotein B molecule, measuring apolipoprotein B in the blood gives a direct count of the total number of atherogenic particles in circulation, regardless of how much cholesterol each one contains.³

The European Society of Cardiology and the European Atherosclerosis Society recommend apolipoprotein B for cardiovascular risk assessment, and regard it as preferable to non-HDL cholesterol in people with diabetes, obesity, metabolic syndrome, raised triglycerides or very low LDL cholesterol.12 Independent analyses go further, concluding that apolipoprotein B is the more accurate marker of atherogenic risk overall.^3,4

A review published in the Journal of Clinical Lipidology, incorporating data from over 593,000 participants, confirmed that apolipoprotein B reflects residual atherosclerotic cardiovascular disease risk more accurately than LDL cholesterol, particularly in people with insulin resistance, obesity or high triglycerides, where the difference between LDL cholesterol and actual particle burden tends to be most pronounced.⁴

Building on this, an analysis of over 40,000 UK Biobank participants followed for at least ten years found that where apolipoprotein B is elevated relative to LDL particle number, cardiovascular risk is higher.5 Apolipoprotein B and LDL particle number are closely correlated measures, but where the two diverge it is apolipoprotein B that carries the risk information.⁵ The practical implication is that apolipoprotein B provides information about atherogenic (heart disease and stroke) risk that LDL cholesterol alone cannot reliably deliver.

What Does Lipoprotein(a) Measure?

Lipoprotein(a), also known as Lp(a), is a lipoprotein particle that resembles LDL in structure but carries an additional protein component, apolipoprotein(a), which gives it properties beyond those of LDL itself.6 What makes lipoprotein(a) clinically important is that it is an independent and causal risk factor for atherosclerotic cardiovascular disease, meaning it increases risk through its own mechanisms and not simply as a consequence of other risk factors.⁶

It raises the risk of heart attack, stroke and aortic valve disease regardless of LDL cholesterol levels, and it remains a risk factor even when LDL is well managed with medication.⁷ It is also largely inherited. Between 70% and 90% of the variation in lipoprotein(a) levels between individuals is genetically determined, meaning that diet, exercise and standard lipid-lowering treatments such as statins have little meaningful effect on it.⁶ No treatment has yet been shown to reduce cardiovascular events by lowering lipoprotein(a), and the first outcome trials of targeted lipoprotein(a)-lowering therapies are due to report during 2026. Knowing the level matters, because it changes how aggressively every other modifiable risk factor should be treated.

An estimated one in five people worldwide carry elevated lipoprotein(a) levels, and the majority are unaware of it because the marker is not included in a routine cholesterol test.⁷ Measuring lipoprotein(a) is therefore a one-time test that establishes an individual’s inherited cardiovascular risk profile. Both the 2025 European Society of Cardiology and European Atherosclerosis Society focused update and the 2026 American College of Cardiology and American Heart Association dyslipidaemia guideline now recommend that lipoprotein(a) is measured at least once in every adult’s lifetime.^12,13 In the UK, HEART UK recommends measurement in those with a personal or family history of premature cardiovascular disease, those with a first-degree relative whose lipoprotein(a) is above 200 nmol/L, patients with familial hypercholesterolaemia, patients with calcific aortic valve stenosis, and those with a borderline ten-year risk score. Results should be reported in nmol/L, with levels above 105 nmol/L regarded as clinically significant.^12,14

What Does Lp-PLA2 Measure?

Lipoprotein-associated phospholipase A2, also known by the test name PLAC, is an enzyme expressed by macrophages and other inflammatory cells, including within arterial plaques. It is a marker of vascular inflammation, and elevated levels are associated with plaque inflammation and instability rather than simply the presence of plaque.⁸

This matters because not all plaque carries the same risk. The plaques most likely to rupture and cause a heart attack or stroke are those with an inflamed, unstable structure, and lipoprotein-associated phospholipase A2 reflects this characteristic precisely. The enzyme circulates in the blood largely bound to LDL particles, and its levels are an independent predictor of coronary heart disease and ischaemic stroke, with the association persisting after adjustment for traditional cardiovascular risk factors including total cholesterol and other inflammatory markers.⁹

A systematic review found that PLAC predicts increased risk of heart attack and stroke in population studies fully adjusted for other cardiovascular risk factors, and that it is useful for identifying individuals at high risk of coronary events who might not be identified through standard risk assessment alone.¹⁰ Building on this, a biomarker analysis within the STABILITY trial, involving over 14,000 patients with stable coronary heart disease, found that higher lipoprotein-associated phospholipase A2 activity is independently associated with an increased risk of major cardiac events including heart attack and stroke.¹¹

Lipoprotein-associated phospholipase A2 is a marker of risk rather than a proven driver of it. Two large randomised trials of darapladib, a drug that directly inhibits the enzyme, found no reduction in cardiovascular events, and large-scale genetic studies of naturally occurring enzyme-lowering variants point the same way.^{15, 16, 17}

Who Should Consider an Advanced Lipid Panel?

Advanced lipid testing is particularly relevant for individuals:

• Who have had a cardiovascular event despite normal or well-managed cholesterol levels
• Those with a strong family history of early heart disease; individuals with diabetes, obesity or metabolic syndrome in whom LDL cholesterol is known to underestimate atherogenic particle burden
• And anyone seeking a more complete picture of their cardiovascular risk than a standard lipid panel can provide.

A single lipoprotein(a) measurement is sufficient to establish an individual’s inherited risk, as levels remain relatively stable across a lifetime. Apolipoprotein B and lipoprotein-associated phospholipase A2 provide ongoing assessment of particle burden and vascular inflammation that can be monitored over time and in response to treatment.

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