ApoB test (apolipoprotein B)

What the test measures and why particles count

Cholesterol does not float freely in the blood; it travels in transport particles. LDL, VLDL and their intermediate forms can penetrate the vessel wall, get stuck there and deposit cholesterol. Each of these particles carries exactly one molecule of apolipoprotein B. The ApoB value is therefore a count: how many potentially vessel-damaging particles are on the move.

Classic LDL cholesterol measures something else, namely how much cholesterol is contained in the LDL particles. Imagine trucks: LDL cholesterol weighs the cargo, ApoB counts the vehicles. Usually the two match; in the UK Biobank, ApoB, LDL and non-HDL cholesterol were very closely correlated. They typically diverge with high triglycerides, diabetes or overweight: then the particles often carry less cholesterol, and according to the European guideline LDL underestimates their number. In that case, an unremarkable LDL can mask a high risk.

In the longevity scene, ApoB is therefore considered the more important blood lipid value. In terms of measurement, there is much to be said for it: the determination has been internationally standardized since 1994, runs on normal laboratory equipment and works both fasting and non-fasting. A separate blood lipid value with a genetically determined level that counts in addition to ApoB is described on the page Lipoprotein(a). Where ApoB stands among the other laboratory values is shown in the blood values overview and the article on the annual blood test.

What the studies show

Ference 2019 – genetics from 63 studies

Mendelian randomization with 654,783 people and 91,129 cases of coronary heart disease. Gene variants in the LPL gene mainly lower triglycerides, variants in the LDL receptor gene mainly LDL cholesterol. Per 10 milligrams per deciliter less ApoB, both lowered the risk almost equally, to 0.77-fold. After adjustment for ApoB, neither triglycerides nor LDL cholesterol had an effect of their own. The authors conclude that the benefit of lowering blood lipids is likely to correspond to the absolute change in ApoB.

Richardson 2020 – which blood lipid value carries the cause

Genetic analysis with data from the UK Biobank and 60,801 cases. Considered individually, LDL cholesterol, triglycerides and ApoB increased the risk. Analysed together, only ApoB remained stable, with a 1.92-fold risk per standard deviation, while the effect of LDL cholesterol disappeared.

Marston 2022 – UK Biobank and two heart trials

389,529 people not taking lipid-lowering drugs, followed for a median of 11 years, plus 40,430 patients with known vascular disease on statins. ApoB, non-HDL cholesterol and triglycerides were each associated with heart attacks on their own, but considered together only ApoB was: 27 percent higher risk per standard deviation. The ratio of particle types no longer changed anything.

Johannesen 2021 – the risk under statins

13,015 people on statins from the Copenhagen General Population Study, median 8 years. If ApoB was above the median but LDL below it, the risk of heart attack was 49 percent and of death 21 percent higher than with both values below the median. High LDL with low ApoB, by contrast, was not associated with more events.

Sniderman 2011 – meta-analysis of the risk markers

12 cohort analyses with 233,455 people and 22,950 events. Per standard deviation, the risk rose by 43 percent with ApoB, by 34 percent with non-HDL cholesterol and by 25 percent with LDL cholesterol.

Epstein 2025 – ApoB against LDL particle number

41,099 UK Biobank participants with at least 10 years of follow-up. Where ApoB was higher than the LDL particle number would have led one to expect, the risk rose with the extent of the deviation, at 30 percent to 1.4-fold for major cardiovascular events and 2.5-fold for coronary events. Conversely, a deviating particle number provided no additional information.

Welsh 2019 – what the test adds on average

346,686 UK Biobank participants without heart disease and without statins, median 8.9 years. ApoB, LDL and non-HDL cholesterol had almost equally strong associations with cardiovascular events. If total and HDL cholesterol were already in the prediction model, ApoB practically no longer improved discrimination, by 0.0004 in the C-index. This is the strongest objection to the claim that everyone needs ApoB.

Where the data stop

For the population average, the gain is small. Because ApoB, LDL and non-HDL usually move in step, ApoB tells most people little that total and HDL cholesterol do not already tell them. The advantage is concentrated in the people in whom the values diverge, and for this the evidence comes from observational data.

The decisive study is missing: no one has randomly assigned people to treatment guided by ApoB or by LDL and counted where fewer heart attacks occur. The guideline’s target values also correspond to the LDL targets; there are no uniform ApoB targets internationally. Mendelian randomization, moreover, measures a lifelong exposure; it does not say directly how much lowering in later years achieves.

Status, approval and legal

ApoB is an ordinary laboratory value requested by a doctor. The European societies ESC and EAS have recommended it since 2019 for risk assessment, especially with high triglycerides, diabetes, overweight or very low LDL, and name it as a possible alternative to LDL for diagnosis and treatment (class of recommendation I, level of evidence C). In the health check-up of the statutory health insurers from age 35, the lipid profile consists of total cholesterol, LDL, HDL and triglycerides; ApoB is not included. Without a medical reason, you usually pay for it yourself. What role it plays alongside statins, bempedoic acid and lifestyle is collected on the page Lowering LDL cholesterol.

Safety

Physically, the test is a normal blood draw, usually together with other values. The real risks lie in the interpretation: a normal LDL can falsely reassure when ApoB is high, and a single high value without looking at blood pressure, smoking, family and other risk factors can cause unnecessary worry. How an additional value affects treatment decisions has hardly been studied. The interpretation and any decision about medication belong in a conversation with a doctor. Anyone who also wants to know whether calcium has already formed in the coronary arteries will find the measurement for this under Coronary calcium score.

Sources

• Ference BA et al., JAMA 2019 — Mendelian randomization: LPL and LDLR variants lower heart risk equally per 10 mg/dl less ApoB (654,783 participants)
• Richardson TG et al., PLoS Medicine 2020 — multivariable Mendelian randomization on blood lipids, apolipoproteins and coronary heart disease
• Marston NA et al., JAMA Cardiology 2022 — ApoB-containing lipoproteins and heart attack risk (UK Biobank, FOURIER, IMPROVE-IT)
• Johannesen CDL et al., JACC 2021 — ApoB and non-HDL show residual risk under statins better than LDL (13,015 participants)
• Sniderman AD et al., Circulation: Cardiovascular Quality and Outcomes 2011 — meta-analysis of LDL, non-HDL and ApoB as risk markers
• Epstein E et al., European Journal of Preventive Cardiology 2025 — ApoB versus LDL particle number in the UK Biobank
• Welsh C et al., Circulation 2019 — classic lipid values and apolipoproteins in the prediction of cardiovascular disease (UK Biobank)
• Mach F et al., European Heart Journal 2020 — ESC/EAS guideline 2019 on dyslipidaemias
• De Oliveira-Gomes D et al., Circulation 2024 — apolipoprotein B: evidence and clinical practice (guideline comparison, standardization, discordance)
• Federal Joint Committee (G-BA) — Health Examination Directive (check-up, lipid profile)