Picture two people with almost identical cholesterol results. One has a parent who had a heart attack at 50; the other does not. A standard lipid panel may not explain the difference, and that gap is where two less familiar markers come in: lipoprotein(a), usually written Lp(a), and apolipoprotein B, or ApoB.
Neither is new to science, but both are still absent from most routine check-ups. This article explains what each test measures, why specialist societies have been paying more attention to them and when people tend to consider them.
What is lipoprotein(a)?
Lp(a) is a particle that looks a lot like LDL cholesterol, with an extra protein, apolipoprotein(a), attached to it. A review in the Lancet notes that Lp(a) concentrations are more than 90% genetically determined (Nordestgaard and Langsted, 2024). In practice, that means your level is largely set at birth and changes little with diet or exercise.
A European Atherosclerosis Society consensus statement concluded that genetic and epidemiological studies involving hundreds of thousands of people support a causal and continuous link between Lp(a) concentration and cardiovascular outcomes, and that high Lp(a) is a risk factor even when LDL cholesterol is very low (Kronenberg et al., 2022). The same review in the Lancet estimates that one in five people have levels high enough to raise their risk.
Why "once in a lifetime"
Because Lp(a) is mostly inherited and stable, the European panel recommends measuring it at least once in adults. It also highlights the value of testing relatives when someone has familial hypercholesterolaemia, a family history of high Lp(a) or heart disease at a young age (Kronenberg et al., 2022). That is why, as a general orientation, Lp(a) is usually a one-off test, unlike cholesterol, which is repeated.
The Lipoprotein (a) test in the BPR Clinic catalogue measures the level of Lp(a) in the blood. According to the LML, results are available one day after the sample reaches the laboratory.
What is apolipoprotein B?
ApoB is a protein that sits on the outside of every potentially harmful cholesterol-carrying particle: LDL, VLDL, their remnants and Lp(a). Each of these particles carries exactly one ApoB molecule. So measuring ApoB is, in effect, a way of counting those particles (Sniderman et al., 2019).
Why count particles instead of weighing cholesterol? A narrative review in JAMA Cardiology explains that the amount of cholesterol per particle varies. Two people can have the same LDL cholesterol carried in very different numbers of particles, and it is the number of particles entering the artery wall that drives build-up (Sniderman et al., 2019).
A 2024 expert consensus from the US National Lipid Association states that ApoB reflects the atherogenic burden more accurately than LDL cholesterol and adds value when used alongside a standard lipid profile. When LDL cholesterol and ApoB disagree, risk tends to follow ApoB (Soffer et al., 2024).
The Apolipoprotein B test in the catalogue measures this protein directly. The LML describes it as associated with cardiovascular risk and useful for monitoring.
And apolipoprotein A1?
ApoA1 is the counterpart on the protective side. It is the main protein of HDL particles. According to the LML, higher levels of the Apolipoprotein A1 test are generally associated with lower cardiovascular risk, while low levels have been linked to higher risk. Some professionals look at ApoB and ApoA1 together to see the balance between the two families of particles.
When these tests tend to make sense
Lp(a) and ApoB are not screening tests for everyone, but they are often considered when:
- there is a family history of heart attack or stroke at a young age;
- a close relative is known to have high Lp(a) or familial hypercholesterolaemia;
- cholesterol results look reasonable but other factors raise questions;
- triglycerides are high, diabetes or excess weight is present, and the professional wants a clearer count of particles;
- someone is already on treatment and their clinician wants another measure to follow.
How often
As a general orientation, Lp(a) is usually measured once in a lifetime, and ApoB once a year when it is being followed. Your history and any treatment change that picture, so talk to a healthcare professional before deciding.
