ApoB: the number cardiologists increasingly prefer

Cholesterol by weight, or particles by count

A standard lipid panel weighs cholesterol. LDL cholesterol tells you how much cholesterol is being carried inside LDL particles — a mass, in milligrams per decilitre.

ApoB counts the carriers instead. Apolipoprotein B is a structural protein, and there is exactly one molecule of it on every atherogenic particle — every LDL, VLDL, IDL and lipoprotein(a). So an ApoB measurement is a headcount of the particles that can lodge in an artery wall.

That distinction is the whole argument. It is the particles that collide with the artery wall, not the cholesterol they happen to be carrying.

Why the two numbers can disagree

Particles are not all equally loaded. Someone with small, cholesterol‑poor LDL particles needs more of them to carry the same cholesterol — so their LDL‑C looks reassuring while their particle count is high.

That pattern is common in exactly the people a metabolic clinic sees: raised triglycerides, low HDL, insulin resistance, central weight. It is the case where a normal lipid panel is genuinely misleading, and it is the reason ApoB has gained ground.

Where the two agree — which is most people, most of the time — ApoB adds little.

What the guidelines say, and how firmly

Several major guidelines now list ApoB as a secondary target or a refinement, particularly for people with high triglycerides, diabetes, obesity or very low LDL‑C. The European Society of Cardiology and the European Atherosclerosis Society have been ahead of others on this.

What has not happened is ApoB replacing LDL‑C as the primary measure in routine practice. Treatment trials were built on LDL‑C, the evidence base for targets is in LDL‑C, and most laboratories and clinicians still work in it. Anyone telling you the lipid panel is obsolete is ahead of the evidence.

Non-HDL cholesterol: the free version

Worth knowing before you pay for anything. Non‑HDL cholesterol is total cholesterol minus HDL — arithmetic you can do on a panel you already have. It captures the cholesterol in every atherogenic particle, and it tracks ApoB closely enough that several guidelines treat it as a reasonable substitute.

It costs nothing. If your laboratory does not report it, subtract the two numbers yourself.

Availability and cost here

ApoB is an immunoassay, which puts it in the expensive half of the price list — the antibody‑based tests that cost two to four times what automated chemistry does. Not every Costa Rican laboratory offers it, and some refer it elsewhere, which changes the turnaround.

It is not in our baseline panel. The baseline is seven markers chosen on one test: would the result change what we prescribe. For most first visits, the lipid panel and non‑HDL answer the question. ApoB goes on when the picture is discordant — good LDL‑C with bad triglycerides, or a family history that does not match the numbers.

If you do have it measured

• It does not require fasting, unlike the triglycerides on the same panel.
• Use one laboratory. Assays differ between platforms, and a change of laboratory can look like a change in you.
• Ask for the laboratory's own reference range. Population percentiles differ, and published risk thresholds are not universal.
• Read it beside the lipid panel, never instead of it.

The boundary

A particle count is a risk marker, not a diagnosis and not a prescription. What any given number means for you depends on your age, blood pressure, smoking, family history and what else is on the panel — and what to do about it is a decision for a physician who has all of that in front of them.