Some people already know their cholesterol numbers well. They have had several lipid profiles, perhaps a Lp(a) or ApoB result, and they or their doctor still want more detail. For that smaller group, the BPR Clinic catalogue includes two specialised tests: LDL7 Subfractions and the PLAC Test (Lp-PLA2).
Both are for going deeper, not for starting out. This article explains what each one measures, what the research says about them and why they are usually ordered with a professional's guidance.
LDL is not one single particle
A standard cholesterol test reports LDL cholesterol as a single figure: the amount of cholesterol carried in LDL particles. But LDL is a mixed group. Some particles are large and buoyant; others are small and dense.
That difference matters because of how particles behave inside the artery wall. A narrative review in JAMA Cardiology explains that smaller, cholesterol-depleted particles bind more strongly to the tissue of the artery wall and so are more likely to be trapped there than larger ones (Sniderman et al., 2019).
What the LDL subfractions test measures
According to the LML, the LDL7 Subfractions test separates LDL into seven subtypes, from LDL 1 to LDL 7, according to size and density, and reports them alongside total cholesterol and LDL. The LML notes that smaller, denser particles are associated with a higher risk of heart disease than larger, less dense ones.
The LML also lists the situations in which the test may add information:
- assessing cardiovascular risk in more detail;
- looking more closely at abnormal blood fats (dyslipidaemia);
- the lipid side of metabolic syndrome;
- insulin resistance, which has been associated with a pattern of smaller LDL particles.
What the evidence says
Small dense LDL is described as an emerging risk factor and a promising biomarker. At the same time, an analytical review from an NHS biochemistry department notes that there is no "gold standard" method to measure it, that different methods are hard to compare, and that its clinical value and cost-effectiveness have not been fully established (Kanonidou, 2021).
That is an honest summary of where this test sits: interesting, sometimes useful in specific cases, and best read by someone who understands its limits. It does not replace the standard profile that UK guidance uses to assess risk.
What the PLAC Test measures
The PLAC Test measures lipoprotein-associated phospholipase A2, shortened to Lp-PLA2. It is an enzyme carried with lipoproteins in the blood, which is where its name comes from. According to the LML, the test is used to assess the risk of cardiovascular disease, particularly atherosclerosis and stroke.
Research on Lp-PLA2 has focused largely on people who already have heart disease. A meta-analysis of 15 studies with more than 30,000 participants found that higher Lp-PLA2 activity or mass was independently associated with more cardiovascular events in people with coronary heart disease, especially those with stable disease (Li et al., 2017). The same analysis did not find a link with overall mortality.
In other words, the PLAC Test is a marker of risk, not a measure of how much build-up there is in the arteries. Its role in people without known heart disease is less clear.
When these tests tend to make sense
As a general orientation, these tests are considered from around 40 in people with risk factors, and always with guidance. Examples include:
- a strong family history of heart disease, with standard results that do not explain it;
- insulin resistance or metabolic syndrome, where particle size may add context;
- someone who already has coronary heart disease and whose specialist wants additional markers.
There is no fixed repeat interval. Talk to a healthcare professional before ordering, so the result answers a real question rather than adding another number.
