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Targets for LDL-C, ApoB and Small Dense LDL

Posted on Tuesday March 17, 2026 in Cholesterol & Atherosclerosis

Medical illustration showing the structure of an LDL cholesterol molecule in cross-section. The spherical particle has a phospholipid outer shell wrapped by a blue belt representing apolipoprotein B-100 (apoB). The core contains cholesterol esters (orange spheres) and triglycerides (wavy lines). A segment of apoB extends rightward to engage with a green LDL receptor (LDL-R) anchored in a cell membrane, illustrating how LDL is recognised and cleared from the bloodstream.

What Your Cholesterol Results Really Mean

Why particle number often matters more than cholesterol mass — and how high visceral fat can mean high risk even when your LDL looks normal.

An article by Dr Edward Leatham, Consultant Cardiologist   © 2025 E.Leatham

For busy people, or to tune in when on the move, Google Notebook AI audio podcast are available for this story beneath.

Every year, people with raised visceral adipose tissue (VAT) have heart attacks caused by oxidised ApoB accumulating within their coronary arteries despite being told their cholesterol is “normal.” This is not a failure of medicine — it is a failure of a single number to capture a complex biological reality.

This article explains the three key markers of atherogenic risk — LDL-C, ApoB, and small dense LDL — what they each measure, and what targets you should be aiming for if you have heart disease or are at elevated cardiovascular risk.

01 — THE PROBLEM Why a Single Cholesterol Number Isn’t Enough

Most cholesterol in your blood is transported inside protein-coated particles called lipoproteins. These include VLDL, IDL, LDL, Lp(a), and HDL. With the exception of HDL, all of them can contribute to the furring of arteries — a process called atherosclerosis.

Traditional blood tests measure the mass of cholesterol carried inside these particles — for example, LDL-cholesterol (LDL-C). But this is a bit like weighing the contents of a fleet of lorries without counting how many lorries are on the road. Modern risk assessment increasingly focuses on particle number and particle type, which better reflect the true biological drivers of cardiovascular disease.

LDL-C

Cholesterol Mass Measures the total cholesterol content of LDL particles. The standard NHS target. Useful but incomplete — especially in metabolic disease.

Non-HDL-C

All Atherogenic Cholesterol Total cholesterol minus HDL. Captures LDL, VLDL, IDL and Lp(a). Available on every NHS lipid profile — a practical first-line marker.

ApoB

Particle Count One ApoB molecule per atherogenic particle. Directly counts the number of harmful particles — the most accurate single marker of residual risk.

sdLDL-C

Most Atherogenic Fraction The smallest, densest LDL particles. Harder to measure but strongly linked to visceral fat, insulin resistance, and plaque progression.

02 — APOB Counting the Particles That Matter

Apolipoprotein B (ApoB) is a protein present as exactly one molecule per atherogenic particle — including every LDL, VLDL, IDL, and Lp(a) in your bloodstream. Measuring ApoB is therefore equivalent to directly counting the number of potentially harmful particles circulating in your blood.

Why This Matters

Your arteries are injured by particle entry, not by cholesterol mass alone. Each particle that crosses the arterial wall carries the potential to initiate or advance a plaque. A high ApoB means too many particles — even if LDL-C appears “acceptable.”

This discordance between LDL-C and ApoB is particularly common in:

  • Type 2 diabetes and insulin resistance
  • Metabolic syndrome
  • High triglycerides
  • High visceral adipose tissue (VAT) — abdominal fat around the organs – very common in men who have a waist to height ratio >0.5.

In all of these conditions, LDL particles tend to be smaller and carry less cholesterol per particle — so LDL-C underestimates how many particles are actually circulating. ApoB cuts through this noise.

03 — SDLDL Small Dense LDL — The Most Dangerous Fraction

Not all LDL particles are equally harmful. Small dense LDL (sdLDL) particles are:

  • Smaller and more easily oxidised
  • Longer-lived in the circulation
  • More likely to penetrate the arterial wall
  • More prone to being retained in the artery wall, where plaques form

sdLDL predominates in people with raised triglycerides, insulin resistance, and high visceral fat. In a landmark study, Mehta et al. demonstrated that many patients presenting with myocardial infarction had normal total cholesterol and LDL-C — yet a predominance of small dense LDL particles was present. This helps explain why coronary events frequently occur in individuals whose standard lipid profile looks reassuring.

Clinical Note

Direct sdLDL assays are not routinely available on the NHS. However, sdLDL burden can be estimated from a standard lipid panel using the LDL-C:ApoB ratio — explained below.

04 — TARGETS What Are You Aiming For?

UK and international guidelines set progressively lower targets as cardiovascular risk increases. The table below shows targets for all four markers, stratified by risk category.

**Alt text:** Table titled *“SCVC Target Table – Dual Units (mmol/L and mg/dL), 2025”* showing recommended lipid targets by cardiovascular risk category. Columns include Risk Category, LDL-C Target, Non-HDL-C, ApoB Target, and sdLDL-C (if measured). Four risk categories are listed: * **Low / Primary Prevention:** Healthy adults without major risk factors. LDL-C <3.0 mmol/L (<116 mg/dL), non-HDL-C <4.0 mmol/L (<155 mg/dL), ApoB ≤1.00 g/L (≤100 mg/dL), sdLDL-C <1.2 mmol/L (<46 mg/dL). * **Moderate Risk:** Diabetes without cardiovascular disease or subclinical atheroma, or family history of premature coronary disease. LDL-C <2.6 mmol/L (<100 mg/dL), non-HDL-C <3.4 mmol/L (<130 mg/dL), ApoB ≤0.90 g/L (≤90 mg/dL), sdLDL-C <1.0 mmol/L (<38 mg/dL). * **High / Secondary Prevention:** Established cardiovascular disease, peripheral arterial disease, or chronic kidney disease. LDL-C ≤1.6 mmol/L (≤70 mg/dL), non-HDL-C ≤2.6 mmol/L (≤100 mg/dL), ApoB ≤0.80 g/L (≤80 mg/dL), sdLDL-C <0.9 mmol/L (<35 mg/dL). * **Very High / Recurrent Events:** Post-acute coronary syndrome or progressive coronary disease with recurrent events. LDL-C ≤1.4 mmol/L (≤55 mg/dL), non-HDL-C ≤2.0 mmol/L (≤77 mg/dL), ApoB ≤0.70 g/L (≤70 mg/dL), sdLDL-C <0.8 mmol/L (<31 mg/dL). Footnote states targets are derived from NICE NG238, ESC/EAS dyslipidaemia guidelines, and ACC/AHA cholesterol guidelines.

05 — THE RATIO Understanding the LDL-C : ApoB Ratio

Measuring sdLDL accurately requires NMR spectroscopy which is expensive and not widely available yet in the UK. Some specialised pathology labs offer it. However a reasonable surrogate is to calculate  a LDL-C:ApoB ratio, which tells you how much cholesterol each LDL particle is carrying. A high ratio means particles are large and cholesterol-rich (Pattern A — less dangerous). A low ratio means particles are small and cholesterol-poor (Pattern B — more dangerous).

This ratio can be calculated from a standard UK blood test of Apo B and LDL-C.  Because ApoB is reported in g/L and LDL-C in mmol/L, a conversion factor of 2.59 is used to bring them into comparable units:

Estimating sdLDL Burden from Routine Tests

When a direct sdLDL assay is unavailable, this calculation gives a practical estimate of particle size predominance:

Note that in Example C, the LDL-C of 2.0 mmol/L looks well-controlled — but the ratio reveals a dangerous small-particle pattern driven by high particle number.

06 — GUIDELINES Why Targets Differ Slightly Between Bodies

NICE, ESC/EAS, and ACC/AHA all set somewhat different thresholds — but they point in the same direction. Think of these as an inter-guideline range, not a sign of biological uncertainty.

NICE NG238 (UK)

Emphasises non-HDL-C and LDL-C targets. ApoB increasingly recognised in high-risk and metabolic phenotypes. Standard for NHS practice.

ESC/EAS 2023

Recommends ApoB < 0.80 g/L for high risk and < 0.70 g/L for very high risk. Most aggressive international guidance on particle-based targets.

ACC/AHA (USA)

Recognises ApoB as a risk-enhancing factor, particularly in hypertriglyceridaemia and metabolic disease. Broadly aligned with ESC at very high risk.

The approximate inter-guideline variation is ±0.10–0.15 g/L for ApoB at each risk tier, and ±0.2 mmol/L for LDL-C and non-HDL-C. The clinical message is consistent: higher risk demands lower particle burden.

07 — THE VAT CONNECTION Why Visceral Fat Changes Everything

Visceral adipose tissue (VAT) — the fat stored around abdominal organs rather than under the skin — is a metabolically active tissue. When VAT is elevated, it floods the liver with palmitate (a saturated fatty acid), driving the production of small, dense, saturated LDL particles.

The consequences are threefold:

  • LDL particles become smaller and more cholesterol-depleted — so LDL-C falls or stays flat
  • The number of particles increases — so ApoB rises
  • The most atherogenic fraction (sdLDL) predominates
The VAT Trap

A patient with high VAT may have an LDL-C of 2.0 mmol/L — apparently well-controlled — yet carry an ApoB of 1.1 g/L and a ratio below 0.8. They look treated. They are not adequately protected.

This is why treating LDL-C without addressing visceral adiposity leaves the metabolic driver of sdLDL production entirely untouched.

Reducing VAT — through dietary intervention, resistance training, and GLP-1-based therapies where appropriate — is not merely a lifestyle aspiration. It is an essential component of complete cardiovascular risk management.

Take-Home Messages for Patients and Clinicians

At SCVC we offer blood testing for LDL-C, LP(a) and Apo B in clinic or via a painless test you can run in the comfort of your own home by post. All of our tests are available with or without a cardiologist report.

Use our contact form to make an enquiry or see https://www.scvc.co.uk/your-health-at-home/

References

  1. Mehta JL, Saldeen TGP, Rand K. Interactive role of infection, inflammation and traditional risk factors in atherosclerosis and coronary artery disease. J Am Coll Cardiol. 1998;31(6):1217–25.
  2. Cromwell WC, Otvos JD, Keyes MJ, et al. LDL particle number and risk of future cardiovascular disease in the Framingham Offspring Study. J Clin Lipidol. 2007;1(6):583–92.
  3. Boekholdt SM, Arsenault BJ, Mora S, et al. Association of LDL cholesterol, non-HDL cholesterol, and apolipoprotein B levels with risk of cardiovascular events among patients treated with statins. JAMA. 2012;307(12):1302–9.
  4. Sniderman AD, Thanassoulis G, Glavinovic T, et al. Apolipoprotein B particles and cardiovascular disease: a narrative review. JAMA Cardiol. 2019;4(12):1287–95.
  5. National Institute for Health and Care Excellence. Cardiovascular disease: risk assessment and lipid modification (NG238). London: NICE; 2023. Available from: nice.org.uk/guidance/ng238
  6. Arnett DK, Blumenthal RS, Albert MA, et al. 2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease. Circulation. 2019;140(11):e563–95.
  7. Mach F, Baigent C, Catapano AL, et al. 2019 ESC/EAS Guidelines for the management of dyslipidaemias. Eur Heart J. 2020;41(1):111–88.
  8. Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC Guideline on the management of blood cholesterol. Circulation. 2019;139:e1082–e1143.
Disclosure: This article is part of The VAT Trap educational series by Dr Edward Leatham and is intended for educational purposes for patients and clinicians. It does not constitute individual medical advice. Targets should be interpreted in the context of the individual patient’s full clinical picture. All treatment decisions should be made in partnership with a qualified healthcare professional.

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