In a rare blood fat disorder called type III hyperlipoproteinemia, heart disease risk comes from leftover fat particles in the blood — not from the usual risk marker. Even if your 'bad particle' count looks okay, these leftovers can still clog arteries, so doctors can't rely on that usual test here.

ApoB is a better blood test for predicting heart disease than standard cholesterol tests because it counts the actual particles that clog arteries, while cholesterol numbers can be misleading since each particle carries different amounts of cholesterol from person to person.

Measuring apoB might give a better picture of heart disease risk than LDL cholesterol because it counts the actual number of harmful particles in your blood, not just how much cholesterol they carry.

Most of the 'bad' particles in your blood that can lead to heart disease are LDL, not the other kind (VLDL), because there are way more LDL particles floating around—even if you have high triglycerides.

Heart disease risk from clogged arteries is more about how many bad cholesterol particles are in your blood — counted by a protein called apoB — than about how much cholesterol is inside them.

If your 'bad' cholesterol numbers don’t all match up, measuring apoB or non-HDL cholesterol might tell you more about your heart disease risk than the usual LDL number — high apoB means higher risk, even if LDL looks low.