LDL-P vs ApoB: Understanding Particle Number in Cardiovascular Risk
Let’s compare LDL-P and ApoB as measures of atherogenic particle number. Learn why guidelines favor ApoB and how Precision Health Reports gives the full picture.
Introduction: Why Particle Number Matters
For decades, cholesterol testing has been the cornerstone of cardiovascular risk assessment. Patients and clinicians alike have focused on LDL cholesterol (LDL-C) as the “bad cholesterol” that needs to be lowered to reduce the chance of heart attack or stroke. But modern research has revealed that LDL-C alone does not always tell the full story.
Two people can have the same LDL-C, yet one has significantly higher risk for cardiovascular disease because their blood carries far more atherogenic lipoprotein particles. These particles are what actually drive plaque formation in arteries.
That’s where LDL particle number (LDL-P) and Apolipoprotein B (ApoB) come in. Both measure the actual number of particles, offering a more precise understanding of cardiovascular risk. While both are valuable, guidelines increasingly lean toward ApoB.
This article unpacks what each test measures, how they compare, and why looking at particle number is critical for understanding true cardiometabolic risk.
Quick Refresher on LDL Particles vs. the Lipid “Cargo” They Carry
What LDL-P Measures
LDL-P refers to the number of LDL particles in the blood. Unlike LDL-C, which measures the cholesterol mass carried inside LDL, LDL-P counts the “vehicles” transporting that cholesterol.
How it’s measured: LDL-P is determined using Nuclear Magnetic Resonance (NMR) spectroscopy, a technology adapted in the 1990s by LipoScience before becoming part of LabCorp.
What it tells us: More LDL particles mean a greater chance those particles will infiltrate the arterial wall and trigger plaque buildup.
Why it matters: Even if the cholesterol inside each LDL particle is low, having more particles increases risk.
Example:
Patient A: LDL-C = 110 mg/dL, LDL-P = 1,900 nmol/L → High number of particles = high risk.
Patient B: LDL-C = 110 mg/dL, LDL-P = 1,100 nmol/L → Lower particle burden = lower risk.
👍 Rule of thumb: When concordant (see below for more concordance discussion) LDL-P will be roughly 10x LDL-C
👍 Another Rule of thumb: When LDL-P and LDL-C differ, cardiovascular risk always tracks with LDL-P.
Learn more about the NMR Lipoprofile lab report included with each Assessment: Understanding NMR Lipoprofile.
What ApoB Measures
Apolipoprotein B (ApoB) is the structural protein on every atherogenic particle, including:
Very-low-density lipoprotein (VLDL)
Intermediate-density lipoprotein (IDL)
Low-density lipoprotein (LDL)
Lipoprotein(a) [Lp(a)] AKA “L P little a”
Every particle carries exactly one ApoB molecule, meaning that ApoB concentration directly reflects total atherogenic particle count.
How it’s measured: ApoB is measured using simple immunoassays, widely available in most major laboratories. Labs ordered at part of a Cardiometabolic Risk Assessment or Advanced Metabolic Health Assessment have the ApoB measurement done by the same NMR technology used to measure LDL-P.
Why it matters: By capturing all atherogenic particles, ApoB provides a more complete view than LDL-P, which only counts LDL. ApoB captures remnant lipoproteins (VLDL, IDL) that matter in people with diabetes, obesity, or high triglycerides — conditions where LDL-P might underestimate risk.
Guideline adoption:
ACC/AHA (2018): ApoB can refine risk assessment, especially if triglycerides are high or metabolic syndrome is present.
ESC/EAS (2019): ApoB is recommended as the primary marker of atherogenic particles.
NLA (2021): ApoB should be used as a treatment target in high-risk patients.
Learn More about the difference between ApoB vs. LDL Cholesterol: ApoB Testing vs LDL Cholesterol.
📚Additional Reading
ACC Expert Consensus Decision Pathway on Nonstatin Therapies
→ Highlights how particle number and ApoB can be used to refine lipid management beyond LDL-C alone.
European Atherosclerosis Society (EAS) Consensus on ApoB
→ Reviews evidence that ApoB is the most accurate marker of atherogenic particle number and should guide treatment targets.
National Lipid Association Scientific Statement on ApoB
→ Provides practical recommendations for incorporating ApoB into routine practice.
JAMA Cardiology: Discordance of LDL-C and ApoB
→ Study showing that patients with normal LDL-C but high ApoB face higher cardiovascular risk underscoring why ApoB is superior.
Circulation: Role of Lipoprotein Particles in ASCVD Risk
→ Explains how atherogenic particle burden drives plaque formation and why particle number better predicts events.
How Both LDL-P and ApoB Relate to Particle Number
Both LDL-P and ApoB are better risk indicators than LDL-C because they measure particle number instead of just cholesterol mass.
LDL-P = counts LDL particles only.
ApoB = counts all atherogenic particles.
Analogy:
LDL-C = weight of groceries in your car.
LDL-P = number of cars on the road.
ApoB = number of all vehicles (cars, trucks, buses) on the road.
The higher the number of vehicles, the higher the chance of congestion. In cardiovascular terms, arterial blockage.
Internal link: Why Measure Cardiometabolic Risk.
Concordance and Discordance: When the Numbers Don’t Match
One of the most important reasons to measure LDL-P or ApoB is discordance with LDL-C.
Concordance: LDL-C, LDL-P, and ApoB all align (either high or low).
Discordance: LDL-C appears normal, but LDL-P or ApoB are elevated. Or LDL-C is high but ApoB/LDL-P are normal.
Example cases:
Patient A: LDL-C = 90 mg/dL (appears fine), ApoB = 120 mg/dL (high), LDL-P = 1,700 nmol/L (high). → Hidden high risk.
Patient B: LDL-C = 160 mg/dL (appears high), ApoB = 90 mg/dL (normal), LDL-P = 1,100 nmol/L (normal). → Lower actual risk.
Discordance is especially common in people with:
Metabolic syndrome
Type 2 diabetes
Elevated triglycerides
Low HDL cholesterol
Want to learn more about measuring Metabolic Syndrome: Understanding Metabolic Syndrome Severity Score.
Why Guidelines Lean Toward ApoB
While LDL-P is scientifically valid and clinically useful, ApoB has become the preferred test for several reasons:
Accessibility: ApoB tests are available at nearly all major labs, while LDL-P via NMR is limited largely to LabCorp’s NMR Lipoprofile assay.
Cost-effectiveness: ApoB assays are generally less expensive than NMR testing when tested outside of the Cardiometabolic Risk Assessment.
Simplicity: Each atherogenic particle carries one ApoB; no complex calculations needed.
Guideline support: Multiple professional societies (ACC, ESC, NLA) endorse ApoB as the most practical measure of particle number.
That said, LDL-P can still add nuance in certain research or clinical settings. Both tests reinforce the importance of looking beyond LDL-C. And, some doctors like the simplicity of LDL-P when looking at individual risk.
Learn more about the relationship between ApoB and Lp(a) for comprehensive risk assessment: ApoB and Lp(a) Testing for Holistic Assessment.
Beyond ApoB and LDL-P: A Whole-Person Approach
While ApoB and LDL-P are powerful, no single biomarker is enough to capture the complexity of cardiometabolic risk. Cardiovascular events result from multiple factors, including:
Age, gender, ethnicity
Blood pressure
Smoking status
Body Mass Index
Diabetes or insulin resistance
Inflammation markers
Genetics and family history
Confounding health conditions
Previous history of ASCVD events
This is why Precision Health Reports goes beyond ApoB or LDL-P alone.
The Cardiometabolic Risk Assessment Advantage
Uses established calculators (such as the Pooled Cohort Equations) as a foundation.
Applies risk-enhancing factors to adjust risk based on real-world profiles.
Provides personalized lipid targets (LDL-C, Non-HDL-C, ApoB, or LDL-P) aligned with global guidelines.
Includes key biomarkers like LP-IR (lipoprotein insulin resistance) to assess upstream metabolic dysfunction.
By combining particle number testing with a whole-person view, the Cardiometabolic Risk Assessment delivers a complete and actionable assessment on an individual’s risk for metabolic syndrome, type 2 diabetes, and ASCVD events such as heart attacks and strokes.
To really zoom out, read more about Why Measure Cardiometabolic Risk
Conclusion
LDL-P and ApoB both represent a leap forward in cardiovascular risk detection because they measure particle number — the true driver of plaque buildup. While LDL-P is scientifically valuable, ApoB is simpler, more widely available, and increasingly guideline-recommended.
But particle number alone isn’t enough. True prevention requires integrating biomarkers, clinical history, and guideline-based thresholds to provide personalized treatment goals.
That’s what Precision Health Reports delivers through the Cardiometabolic Risk Assessment: a holistic, evidence-based, and actionable framework for managing risk and preventing devastating events like heart attack, stroke, and type 2 diabetes.
Order your own Cardiometabolic Risk Assessment today and take control of your health with the most advanced, personalized risk evaluation available.
Frequently asked questions about Atherogenic Particle Number
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DescriptLDL-P measures the number of LDL particles in the blood using NMR spectroscopy, while ApoB measures the number of all atherogenic lipoprotein particles (including LDL, VLDL, IDL, and Lp(a)) using an immunoassay. Both reflect particle number, but ApoB is broader and more widely available.ion text goes here
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ApoB is simpler, less expensive, and widely available in most clinical labs. Each atherogenic particle carries one ApoB protein, making it a direct measure of total particle burden. Major societies such as the ACC, ESC, and NLA recommend ApoB over LDL-P for routine practice.
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LDL-P may provide additional detail in research settings or complex lipid disorders where particle size and subclass distribution matter. However, in most clinical settings, ApoB provides the same risk information in a more accessible way.
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Discordance means LDL-C appears normal, but ApoB or LDL-P are elevated. This indicates hidden cardiovascular risk. Discordance is common in people with insulin resistance, type 2 diabetes, or metabolic syndrome.
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LDL-C measures the cholesterol mass inside particles, not the number of particles. Two people can have the same LDL-C but very different particle counts — and the person with more particles has higher cardiovascular risk.
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Precision Health Reports integrates ApoB (or LDL-P when requested) into its Cardiometabolic Risk Assessment, along with other biomarkers and clinical factors, to provide a personalized risk score and individualized treatment targets.